Hello seichel,
I also struggle with SSA. I could be wrong, but I think autism effects a person's ability to communicate and be social. Maybe this is why he has trouble processing what you tell him. Once again, I maybe totally wrong. Its just a thought I had.
Also, its is inaccurate to label people as 'gay' or 'straight'. The idea of labeling people with a single desire has only existed in modern Western cultures. Even the ancient Greeks and Romans, who did not look negatively SSA, didn't think this way. It is better to say 'I have desires for man and/or women' than to say 'I am gay/striaght'. In the former, you are stating emotions that you have. In the latter, you are stating what you are. If you look at things this way, then 'gay' people can get rid of SSA with therapy, just as depressed people can get rid of depression.
I hope that what I have said helps you. I have lust towards men and women, so I know how confusing it is. Feel free to message me anytime.
--some_guy/Elias/Eliyahu