Why are there successes (albeit very little) in "cureing" if there is a gay gene?
In short there probably aren't. The 'ex gay' movement is almost entirely religious asking gays to pray, to abstain or to 'go through the motions' with someone of the other sex. The fact that so many go through the process and say it didn't work probably gives a big clue. Ask any 'ex gay' and they will say that it works...until they come out and say it didn't work and it was a sham as many do and continue to do. That's exactly the same attitude you would get from a Scientologist saying 'yes it cured my depression!'....until they also come out and say it doesn't work and the whole things a con.
There are those who have almost exclusively gay experiences then have almost exclusive straight ones later in life. The opposite is also true. Human sexuality is pretty fluid for some people. For others it's very black and white.