Oh please, the old line of it just being a BJ - he's told you that to make it sound as basic as possible, it's to hide what actually did happen. I don't believe it for a second, what woman would do that unless she was either getting paid, was out her face or was being forced - is he Brad Pitt, no I didn't think so.
You have 3 issues going on here, the fact he has been lying to you for 8 years, the fact he is still lying and the fact, even if his story was true, he has cheated on you - enough to end a relationship I'd say.
You can't trust him now, simple as that, and you've to get over it, really, what a bloody cheek, just shows how sorry he is, not.
Do not brush it under the carpet, talk for as long as you need, he needs to feel the consequence of his actions, if he loves you he will stick it out and he is the one who needs to work on you, there's nothing for you to work on, it should all come from him, you are the innocent!
Don't agree with you having to save anything - why do you have to put any bloody leg work in, you have done FA wrong.