The "Zadok" thing sounds like the "Black Hebrew Israelites" based in NYC. Definitely a sad and twisted ideology IMO.
Generally I agree with what your post is saying, but I think a couple of things should be taken into consideration.
(1) "Ethiopia": in the earlier days of (this present-day incarnation of) Rastafari, the word "Ethiopia" referred to the whole continent of Africa. (As the Bobo *Ashanti* make clear by calling themselves Ethiopia-Africa Black International Congress). So in defining themselves as "Ethiopians" early Rastafari people were defining themselves as "Africans" referring to the whole continent not only the place that was known at the time as Abyssinia.
Certainly there were many Rastas in the early phase of the movement who tried their best, given the resources available to them, to gain knowledge of African cultures in general, not only Amhara/Abyssinian. Read Douglas Mack's autobiography, he talks about the 1961 mission to Ethiopia he was on where he met His Majesty, they also went to Kenya and stayed with traditional Kikuyu people, Mack emphasizes what a brotherly reception they got from the Kikuyu, and how he loved and respected the Kikuyu culture as he was introduced to it, making no mention of so called "pagan" belief systems and no demand that the Kikuyu people abandon their traditions and become Haile Selassie-worshipping Rastas after the Jamaican conception. Let's not forget that Rastafari people in JA were at the forefront of demonstrations etc. in support of the Mau Mau movement (Peter Tosh's first arrest was for taking part in one such demo).
(2) While the inferiority complex, color complex and Judeo-Christian background prevalent amongst caribbean Africans no doubt had something to do with the reasons why some caribbean Africans felt comfortable "worshipping" the brown-skinned head of a monarchy that had something in common with the European monarchies that we had lived under, who was connected to Judeo-Christian roots... I doubt that this was the main reason why most Rastas decided to make H.I.M. Haile Selassie I the main focus (at least, main symbolic focus) of their belief system. I think it had more to do with (a) Abyssinia/Ethiopia being the only uncolonized nation in Africa and hence serving as a symbol for all of Africa, (b) Haile Selassie's claimed lineage from Biblical times- obviously related to absorption of Judeo-Christian concepts, but let's not forget that as far as early Rastas were concerned, the Hebrews who wrote the Bible were not considered to be Semitic people at all, they were considered to be Black Africans. Not saying that that is the idea that best fits the evidence we have available now, but that was the prevailing idea among early Rastas to the best of my knowledge, and is still quite prevalent today. (c) The coronation of Haile Selassie and the psychological effect of witnessing their European overlords bowing and paying homage to an African king who, however light skinned, would certainly have been placed in the category of "inferior black people" had he lived in the west at that time. This of course conjoined with the prophecies of Revelation, Isaiah etc (which you might dismiss as coincidences, etc, but which were not considered so at the time, especially not by people who considered the Bible to be a book originally written by their (black) ancestors, which had been mistranslated, edited and distorted over time but still contained the truth hidden within it if read "with the right spectacles".) Not forgetting of course Marcus Garvey's alleged statement to "look to the east for the crowning of a black king". (d) Mussolini's invasion of Abyssinia, and Haile Selassie's exile and addresses to the League of Nations as the only representative of Africa at that organization. His remarks were considered prophetic of ww2, his exile and subsequent re instatement taken as reflecting still another passage of Revelations, and the conflict with Italy dramatized the overall conflict between good and evil that the Rastafari worldview sees as taking place in the world, and in people's hearts and souls: Mussolini and Pope Pius representing evil, especially representing the European distortion of what were considered to be originally African concepts, and Haile Selassie and the Ethiopian patriots and diaspora black volunteer forces (which were considerable, many diaspora africans volunteered to fight to defend Ethiopia) representing the orginal African root of these concepts. Finally (e) Haile Selassie's visit to JA during which he did not repudiate the rastas as the british and jamaican gov'ts wanted him to [as proven by recently released british intelligence documents revealing that that was a big reason why britain actually tried to pressure Jamaica into inviting His Majesty, in the hope that he would publicly discredit the rastas and defuse what was (correctly) seen as a subversive movement]. Not only that, he invited rastas from the ghetto to his official functions, much to the chagrin of the official functionaries, and referred to Ethiopians and Black Jamaicans as "blood brothers".
Also while it is true that most diaspora Africans come from West/Central Africa, there were some brought from East Africa as well.
Now as far as some new-generation rastas are concerned and certainly as far as many "white rastas" are concerned, I think your arguments hold a lot of weight, but I'm not at all sure that early Rastas tended to embrace Haile Selassie as a godhead because of the psychological problems identifed in your post. I think it had more to do with the factors outlined above.
Also when talking about traditional African "religions", consider how much that is traditionally African was incorporated into Rastafari from the earliest stages, albeit tending to have a judeo-christian veneer as would be expected for a society steeped in judeo-christianity. Concepts like Word-Sound-Power (Nommo), a divine/human ruler (Pharoah), who sits on a "golden throne" (golden stool of the Ashanti), the blurring of distinctions between divine and human ("man is god and god is man" was as much a part of early Rasta teachings as that "Haile Selassie [specifically] is God"; compare to how the divine or semi-divine orishas of your cultural tradition were (as far as I understand) considered to have been once ordinary humans like you and I who distinguished themselves through great deeds and eventually acquired a divine status), drumming as a generator of spiritual power that could heal or kill, identifying with a "totemic" animal (lion), looking to the natural world for guidance and inspiration on how to run human society, etc. I would say that similar to Voudoun, Candomble etc the Judeo-Christian elements were (at least at the start) more of a veneer over an African core, than the essence of the movement. Nowadays we see two tendencies, one to emphasize the Judeo-Christian aspects and de-emphasize the African ones (as exemplified by, for eg. the Twelve Tribes of Israel, or at least by many of its members) and another to emphasize the African elements and "purge" rasta of the judeo-christian elements (as exemplified by people like Mutabaruka, the admin of this board, and perhaps yourself if you identify as rastafari). But originally it was all mixed together to an extent, and again remember that as far as the early Rastas were concerned, Judeo-Christianity *was* at root a traditional African concept that they felt had been hijacked and distorted by Europeans.
I certainly know quite a few rastas who hold fast to concepts like "Haile Selassie is the almighty in flesh" but certainly do not seem to be "ashamed" of their Blackness, in fact promote Blackness to the fullest, some of whom might even look at me with a bit of distrust because I am light skinned, at least until they know me; what I'm saying is that holding fast to ideas such as Haile Selassie being the Almighty in flesh does not *necessarily* presume a privileging of lighter skinned/ "more civilized" Africans over darker skinned/"more primitive" Africans, or put it this way, I am sure there are traditionalist Haile Selassie-worshipping Rastas who worship Haile Selassie IN SPITE of his lighter skin color, not because of it.
Don't want to give you the impression that I strongly disagree with your post cos I think you make a lot of valid points actually- but just providing some alternative/complentary explanations as to how H.I.M. became a central focus of this movement, cos I don't think it's fair to many foundation Rasta people, or to many traditionalist rastas today, to ascribe it entirely or mainly to the color complex and racial/cultural inferiority complex that you seem to be ascribing it to.
PS as far as relations with continental Africans, I've never heard any Rasta people spout the kind of crap that "Zadok" "Black Hebrew Israelites" etc. do. Not that there are not Rastas and caribbean africans in general who have some prejudices to those from the continent (and the reverse does also apply). But actually in terms of the type of prejudice some african caribbean rastas might have to continental people, from remarks that I personally have heard, it's not so much about continental Africans being "pagans" or whatever, or too dark skinned or too "primitive", it's about them not being militant enough. There is a perception that because we been through slavery we got "blood in our eyes" and will not take any kind of crap especially from white people without a strong and often violent reaction, whereas there is a perception (an incorrect perception IMO, but it is there) that continental Africans tend to be "softer" and allow Europeans to run rampant on the continent with little resistance.
Well that is just some points to add to the discussion, again in general I agree with you pretty much, but with the qualifications outlined above.