I cant possibly agree. Saying you disprove of something to me means you believe it's wrong, which is completely different from just personally finding the act of a bit icky. I'm gay and I often find that many people don't really understand what homophobia actually can sometimes be. People will always put you down about it and these people could be your best least offensive friends. My opinion of this topic is it might not be direct homophobia but it's prejudice purely on my first statement. Anyway the thought of straight people doing anything makes me feel sick and repulsed, what would people say to me if I said I disagreed with it? I cant disagree because it's not wrong?
Yes, I think he is homophobic. If as you say he's perfectly fine with gay rights and doesn't want to make things difficult for them then I have no problem with him, but I'd still say it's a homophobic point of view.
I think some people are conflating having a different preference for something with a belief that a particular preference is in some sense objectively wrong/worse/worthy of disapproval/etc. For example, I'm a straight man. I personally am a bit disgusted by the idea of having sex with another man, just as I imagine many gay men are a bit disgusted by the idea of having sex with a woman. I don't 'disapprove' of their preference, I just acknowledge that it is different to my own.
Cheating is not in the same bracket. I agree that it's a personal matter and not something the state should intervene in, but here I'd say there is clearly a 'correct' answer and that's being truthful and faithful to your partner.