Should I date other guys? Or cheat? Or just wait it out?

In about 3 months it will be 2 years "on" for me and my boyfriend. We've been on and off since we were 14, but the last 2 years we've been really committed and monogamous. But a couple months ago he got into a fight defending his stupid *** friend and got locked up. I was there and i saw the whole thing. He wasn't involved in the initial argument, but got sucked into it to defend that idiot friend of his. Long story short, he's going to do between 12-22 months. We won't find out for a couple weeks. But the problem is I don't know if i should stay with him (faithfully), fully break it off with him, or stay with him and just date a little on the side. I know a lot of people hear prison and go "OMG, your stupid!" or "Oh he's worthless and you're dumb if you stay with him!". I've heard the same damn insults and remarks from people who have one image of a criminal in their mind. So if you're one of those close-minded biased people please don't respond (Thanks:D). Anyways, he's a really good boyfriend and he's always treated me like i was angel and made me feel so good inside. He's been in trouble before and was on probation when he got incarcerated. On the other hand, he was almost off of probation, had gotten back in school, was staying out of trouble, and getting his life back on track. Reading this back to myself it seems like i've already made my decision to stay with him, but a part of me just isn't sure. I'm just still so ****** mad at him for trusting his friend so much to do the right thing. And it just makes me even more furious the fact that he stood up for him!!! He knows he ****** up and he's beating himself up about it (trust me), but i don't know if that's enough for me. My heart loves him so much because he's really my best friend. But then my mind keeps telling me to take advantage of this abrupt freedom and really see what's out there since i've onlt been with him for so damn long. My sister tells me to stay with him but to date around because i'm not married and he'll probably try to lock me down when he gets out so i'll have no other chance lol. But i'm not the cheating type (like i said we were monogamous). And he even told me he'd rather have me break up with him then cheat on him. If i cheat, then what's the point of staying with him? Then i'll have to deal with the guilt and betrayal on my shoulders. But i can't leave him because i know he's depending on me so much. Keep in mind we've been tight since we were 14 so i know he doesn't really have anyone besides his mom and dad to support him. (Like I told him, thousands of times, his friends won't even remember his name when he's locked up or gone! And sadly I was right.) As you guys can see i've really, really sat down and thought about this hard as hell. But i still can't decide what to do. If you were in my shoes what would you do? Help me! (sorry it's lengthy, it's all been bottled up!)