I’m not sure how this theory isn't more popular, but I don’t know about the response to hot women being a gay thing. My personal theory is thusly, and is twofold-style:
1. Phil uses these situations as a backwards way of fostering the image that he only has eyes for his wife, which makes him a Good Person and a Serious Machoor Adult (a point that is regularly argued).
2. Phil has a combination of sexual dysfunctions that make him deeply insecure and uncomfortable when faced with sexual situations in media (I don’t see many people share this sentiment).
I find it likely that Phil has ED. I think it’s a near certainty that he and Kat are not intimate. I also think Phil is a disgusting weirdo that nobody would have a good time being intimate with. I think Phil realizes this, and it makes him feel shame and discomfort when he sees or discusses heterosexuality. I personally think this is much more likely than him being gay. I think he uses gay scenarios to sperg out and crack jokes because he still thinks that making fun of gay stuff in the most generic 2008 way possible is funny, and that since he isn’t insecure about actually being gay he feels comfortable enough to address it rather than shutting down completely like a fucking incel when it involves women, who he knows judge him in a way that even he himself recognizes is objective.