I don't know if there is really any way to know the absolute whole truth when dealing with a pathalogical liar and a serial cheater.
It's almost like you are dealing with two (or three) different people. Serial cheaters who are able to be married and compartmentalize their cheating are a tough nut to crack.
He is going to SAY what ever he thinks you want to hear. But the reality is, you have NO IDEA what (or who) he is really doing behind the scenes.
If you were dealing with a WS who was being completely open, transparent, and remorseful, that would be one thing. But this appears to be a WS who only admits to what you know. And he only offers "trickle-truth" when he is confessing. This is not remorse.
You are dealing with multiple OP's and now multiple d-days. Why are you so desperate to work this out, when he has been the big screw up in the marriage?
My advice to you would be to take a giant step back. You need to regroup and realize that you can't "wish" this marriage to be better. He needs to take the lead. My bet is if you take a step back in the "fixing" he will drop the ball a resume he regular behavior. His ACTIONS after you step back will tell you your next move.