Just my $0.02 here. No one's relationship is perfect, so keep that in mind.
Personally, I'm married to an omni. While I don't like him eating meat and don't approve of his choice (I also feel very strongly about the choices I've made and the lifestyle I live), I've basically resigned myself to the fact that it is
his choice. I've given him the information he needs to make an informed decision and he's made his choice. He's receptive to eating the foods I make (he enjoys most of them although tofu is a no-go with him) and he's supportive of my choice, but it's not something he's willing to make a lifestyle for himself.
I've made it clear that I won't touch any meat and won't cook it for him (the exception is if he puts together a grilled cheese and turkey sandwich or something, I'll cook it since he's not good in the kitchen). If I'm cooking, he's eating veg and that's that.
But I understand your being upset about your boyfriend's inability to get on board with you. I think it was easier for me since my husband and I have been together for far longer than I've been a serious vegetarian (I tried and failed at being veg around the time I originally started dating him--about 9 years ago), so I can't (and shouldn't in my opinion) expect him to change his life around just because I've had a moral awakening with regard to what I'm eating.
Compromise is what works for us, but if you're completely against being in a relationship with someone who isn't willing to go veg*n, you're probably going to have to accept that you're going to have to move on. Your priorities are going to make the final decision. Staying in a relationship when you have a deep moral divide over an issue that's important to you like this is probably isn't going to work unless you're willing to compromise.
As much as that may hurt, you're not going to be doing either one of you any favors if you're staying in a relationship where you deeply disapprove of his choices and aren't able to accept the ones he's made. It's a matter of priorities. Does he matter enough to you that you're willing to live with his "imperfections" and choices you don't approve of/agree with? Or do your commitment to the vegan lifestyle and your moral feelings about his omni diet trump your feelings for him?
I don't agree with my husband (or parents) by any means when it comes to diet, but I've been willing to accept them with their choices. But that's a very personal decision. Of course, I couldn't dump my parents regardless and it would seem strange to me to dump my husband because he made the same choice as them (although I suppose it would be understandable since I have a choice in that issue and have chosen to be with him).
I'm not saying that every veg*n out there is going to be able to make a compromise like I have. Or that I'm in the right. I'm sure some people would feel that I'm not being a committed enough vegetarian to tolerate my husband's omni diet, but I've found a balance I can live with. I also agree that it seems that you've made up your mind and what you end up doing will ultimately depend on what feels right to you. I can't tell you how to live your life or whether to compromise. If you haven't already weighed the options, I'd recommend you do that before making a final decision, but you seem like you've already come to a conclusion on your own and that's your call.