"Homophobia" - yes, that is an annoying word, but there's probably not much to do about it. Didn't the old Sanskrit linguists have a term for that, by the way - the compound that leaves out an element as in "homo(sexual)phobia"?
Perhaps the best solution would be for English to give up its Latin fetish, and go with "gay-phobia" and "anti-jewish" or something. But then of course we might also whine about the misuse of "gay". It's peculiar, by the way, how a word for "happy" came to mean "homosexual". On the other hand we have in Swedish a word that apparently used to mean "homosexual" but now means "angry".
As for "gender" - I know, but personally I don't like the current standard usage. First, because "sex" nowadays usually refers to the activity, which can lead to confusion. Second, because the division in "sex" and "gender" clearly is an attempt by the social-causes theorists to encode their views in the language. (The opposite use of course similarly encodes the opposite view, that I don't deny.)
Your idea for group marriages as a combination of marriage and blood-brothership is nice. It seems realistic even if there is little evidence of anything similar in the real world.
My own conpeople also have a sort of group marriage, but it works like extended polygamy; one man has several wives and several servants who are also as part of the family.