Be completely honest. Stringing him on id you think it won't work won't make you or him feel happier. If you truly believe that something is there and can make it work, then go for it. But don't make yourself unhappy because then he'll give up and you'll just be more unhappy. If you want to try to work it out, try trusting in him. He may be sorry and wants to try harder, but that won't happen if you don't give him the second chance. The decision is yours, but if you want to try to make it last then give him a chance. If not, then be honest with him and let go, but do it gently, because he still has feelings too.

For your well being and for his I think its better if you seperate. He needs to go and figure out what he really wants, and he needs to learn how to do that before starting something up with someone and then hurting them later.

If you choose to take him back, if he comes back after figuring out what he wants, then you'll need to stop agonizing over trusting him so that he can have a chance to rebuild your trust in him. If you can't do that then I would advise against being with him anymore.

Lastly, to a degree we all do this although we try really hard not to, but you need to take an honest look at how he is taking out his stress and frustrations regarding his problems on you. If its bad enought that you are asking for advice then I'd be concerned about him. He may not understand how to deal with stress or, at worst, this could be the sign of an abusive mentality. Like I said, we all snap at our SO at some time or another when they didn't do anything wrong, but we try our hardest not to and apologize for it as well as work on fixing the problem immediately. It doesn't sound like this is happening.