Sarcastic comments really hurt.

SO and I are already on shaky terms relationship-wise, but I decided to try to work it out rather than breaking up.

However, there's one thing I can't stand - if he's angry, he'll either get quiet/moody, or he'll start slinging sarcastic remarks at me that really hurt.

The quiet/moody thing has been there all along, and I've accepted it as just who he is - but the sarcastic remarks thing I've just been seeing in the past few days and it really, really hurts. He'll apologize after a few hours, but it keeps happening and I've pretty much stopped forgiving him.

I kind of want to talk to him about it, but I'm so angry/hurt from this morning that I just want to say "screw it" and break up. I suppose it'd be fine if it was every once in awhile, but I really can't stand him getting upset with me every single day and feeling like I don't do anything right, on top of the problems we're already having.

Has anyone been in this situation, and what did you do?

I think you are already on the right path...its stops or its over. A toxic relationship will bring you down faster and harder than no relationship.

Hmmm. I am sorry this is happening. Have you tried to sit him down and explain to him that these sarcastic remarks he makes hurt you. Try it. If he refuses to sit and listen and try to refrain from the remarks, then I would run.