Kay, (I know I am repeating) I think you need to decide what you want, and I think you need time and space to decide what you want.
I would get him to move out for a month, it would show you both what there is to lose, it would certainly show if there is any love still there between you. You'd need to be strong though, and if after a week it seems clear that you do want to still be together, don't let him back before the end of the month. You need a month (at least) to really experience what it would be like without him. How you'd handle things practically, the boys, money etc. If it's a case of that you're staying with him now for fear of what it would be like without him then you'd find out. If you miss him like crazy as a husband then you'd find that out.
Also, as much as I am guessing it would be nigh on impossible, I'd try not to dwell on what else he might have done, yes protect yourself, don't become his doormat, but from all the time I've 'known' you and from what you've said about him over the years, he doesn't strike me as the type, and if you're going to give it another go, then whilst it is important that you are both honest with each other, it'll never work if you're secretly punishing him for something he in all likelyhood hasn't done, and for something that he knows nothing about.
FWIW, there is no shame in separating/divorcing, there is also no shame in him holding his hand's up, admitting he's done something that is unarguably wrong, and you both working together to get over it, it doesn't make you weak, and it doesn't have to mean that he'd do it again, some people, even men, can learn their lessons.