I definitely think it was a factor, especially (from what we've been told anyway) when the jocks "screwed the best looking girls", and got special treatment. And jocks are usually very traditionally manly.
Eric did rip on himself for being too thin, and he got teased for it too (like the whole head too big for his skinny body), and he probably felt like the only way to get a girl was to look and act like they did. Why else couldn't he get any and they could?
His dad was an army man, and men from the army have to be cold and practical, strong, their work requires that from them. I think Wayne tried to enforce some of that onto Eric, maybe to prepare him for the outside world and the struggles of it. And he lived in a traditional home, where from all accounts it seemed like Wayne truly was the head of the house and Kathy the good wife that stood by his side. So he's getting signals from both school and home, that the only way for him to be accepted is to be a strong alpha male. And with DOOM, where the character is blowing up zombies and such, he longed to be that strong man.
But like you said, he seemed very cordial with the girls around him. Complimenting them, walking them to class. He was smart, and I defiantly think there were times where he felt limited by a mold he wanted to fit in. And it didn't help that Kevin was all that, he had a good social life, was a bit of jock, and got girls.
He tried to open up about his struggles with being picked on, and struggles with girls, but only with girls, never with guys. I think this shows how he wanted to keep up a facade, of not being hurt, of being a man that could handle it.
Eric has issues with wanting to be one thing, what was socially accepted as the prime of a man, and being another. He was thin, not muscular, he was a bit dorky and weird, not charismatic and well liked (hello Dave), he had a weird taste in music and wore black cargo pants with german band t-shirts. He talked about natural selection, and wanting to aid it. And he ultimately killed himself, and I do think he thought he deserved to die as much as the rest of the school.
I don't think Dylan cared too much, he didn't seem like he was trying to fit in at all (like the ring, duster, unkept hair...), and I doubt toxic masculinity played a role, he probably thought the jocks were neanderthals with no self awareness.
Him shoving a girl could have been nothing personal at all, maybe he was just having a particularly bad day and she was annoying him. I agree that Laurens table was hit more bad than usual, but then again he went up and shot lance kirklin in the face so it could've just been a coincidence.