The only thing I would disagree with you on is that I believe that homosexuality is an emotional disorder, not a mental disorder.
Most of the people I know who are homosexual tend to very intelligent (i.e. there is nothing wrong with their mental capacity). It's just their emotions that are screwed up (no pun intended).
From my anecdotal observation, homosexual males tended not to have had their father (or a close male role model to emulate) living with them or participating in their daily lives, leaving their mother to become their person to emulate and pick up their traits---hene, the effeminate personality and mannerisms.
By the same token, I have noticed from anecdotal observation, that homosexual females tended not to have their mother (or a close female role model to emulate) living with them or participating in their daily lives, leaving their father to become their person to emulate and pick up their traits---hence, the "butch" personality and mannerisms.
Since your personality is basically developed from 0 to 5 years, the person would not remember ever feeling/acting anything other than the way they have learned from example. They would tend to believe they were "born that way" even though it was a learned behaviour.
My point is that it is my anecdotal opinion that those who grew up without the benefit of a same-sex role model from early life, didn't choose to be homosexual, but they were not "born that way."
Also, it is not what a homosexual person does in their bedroom that is the problem. Indeed, if they never told us, we would never really know! It is the behaviour they choose to exhibit in public that is the problem.
I guess I don't mean a mental illness like schizophrenia. And I was a bit flippant. However, I do believed homoseuxality is a mental disorder, which I supposed could be describe as an emotional disorder. But, it might be more than that. It begins with failure to establish the correct gender identity, as you note. It carriers with it a whole lot of other baggage, besides just same-sex acting out. Satinover and Nicolosi have done excellent work in this area. Beyond psychology and psychiatry, I believe homosexual practice is "intrinsically disordered" from a Christian perspective, to quote the Vatican.