Boyfriend with internalized homophobia

I’m in a bit of a silly situation that I don’t really have anyone to talk to about, since the country I live in is quite homophobic, and I don’t want to share this with the people in my circle. Just to clarify—I’m a woman. Here’s the gist: I have a boyfriend, let’s call him “F.” We’ve been dating for a while, but we’ve known each other for about eight years. As teenagers, we were always hanging out in the same groups, so we knew a lot about each other even before we started dating. In our circles, it was “common knowledge” that he had certain “tendencies,” but we were all young back then, and most people, even negatively-minded ones, turned a blind eye to it.

He’s had a couple of romantic interactions with men (that almost led to sex) that he’s ashamed of. When we first started dating, he reacted very emotionally to this topic, saying that back then he was “just lost”, but recently admitted (in the context of another topic) that he has “issues with his orientation.”

Overall, he’s much more tolerant than the people around him; he doesn’t feel any hatred toward gay men, but rather a fear that he himself might be somewhere in the middle of the spectrum. I am bisexual myself and went through a rather long and difficult process of coming to terms with it, which he knows about and accepts calmly. Recently, he saw teenage boys who were clearly in love with each other in a public place and was worried that this might have negative consequences for them. He has a bit of an fixation on "gay jokes," he often unconsciously sexualizes interactions with men, avoids shared showers at work, and his main "no" regarding men is "they have stubble and a penis."

This whole situation was sort of in the background and didn’t have much of an impact on his life until I suggested the idea of a threesome (something I’ve wanted to try for a long time and, being single, had made unsuccessful attempts to do, which he knew about and initially, even before our relationship, found the idea interesting). He’s not the type of person who can casually have sex with “just anyone”; the main criterion he set for a potential third partner was trust. Of course, this is taking into account the fact that he doesn’t want a man as the third person, which he has stated more than once.

Going through his acquaintances, he put forward four candidates, one of whom “suddenly” happened to be his friend, let’s call him “P.” “P” is a man. He couldn’t even explain this choice to himself. And, to be honest, I had suspected for some time before that “F” had a suppressed attraction to “P,” because his behavior around him and the general atmosphere of their interaction were quite telltale.

Even before the discussion of the “candidates,” “F” agreed to do a new tattoo for “P” (since he used to do this regularly, though he hadn’t done it for a couple of years and had been turning others down), but after the discussion about the threesome, “F” started avoiding even working on the sketch, even though a month had already passed since they’d chosen the references. Moreover, he has almost stopped mentioning “P” (even though he used to do so frequently), doesn’t answer his calls, and has become much more fixated on homosexual subtext even where there isn’t any.

Considering that I personally don’t get along very well with “P” (he made a very negative first impression) and “P” himself knows that I don’t have positive feelings toward him, it’s fairly easy to predict his thoughts regarding why his friend suddenly started ignoring him. "F," meanwhile, is gradually accumulating feelings of guilt and shame for not even finishing the sketch, yet still not getting down to work on it. And it turns out I accidentally triggered a “turning point” because of which “F” now perceives “P” only in a sexualized context (he now mentions him only in that context) and can’t contact him because of it.

And I have no idea how to help him, because my own path was very different in many ways, plus I have a different gender socialization, and in our country, society is more "tolerant" toward women who are attracted to their own sex than toward men who are attracted to men. "F" is clearly struggling and trying to avoid all of this, but it’s hardly succeeding, and on top of that, yes, it’s quite destructive.