Your brother is an Angry Teenager (or mbe young adult now, but same thing).
Based on your post, it seems he was (as us old farts used to call it) 'cruising for a bruising'. Looking for a fight, in other words.
Ultimately, he needs to be distracted from his trigger (this gal). But, as we have discussed before, when emotions go up, intellect goes down. For you to effectively help, LW, you need to let him vent his emotions. This can be simply listening, without giving advice (at least initially) or perhaps doing some physical activity with him. Do you two box? Or do some martial art? Sometimes, just beating the shit out of *something* (not someone) can help.
Then, once he's got some out of his system, you can make suggestions like 1) he get a part time job to increase his income, and 2) he go out & socialize to find a new girl.
Oh, and you might want to suggest to him that, in a college town, gossip travels. So, if he wants to ever have the chance of dating another girl, he should control himself better. Let him make the rest of the obvious connection to his behaviour.
Good luck, LW. Having had a sibling go through a difficult 'coming out' period, I feel for you. Do your best to relate w/o coming across as 'superior' tho. B/c that will only increase his stress & will not, ultmately, help him. You want him to feel comfortable coming to you.
Oh, and don't forget that, ultimately, its his life. You can only help so much. He has to want to help himself. Don't become your brother's codependent. You are NOT his keeper.