Last night I caught them in a bar together – he said it was just work and this time swore he would “stay away” from her because it upsets me and he wants to work on the marriage. I have heard this before.
First, how did you happen to catch them together? Were you trying to? Have you been snooping on him, following him and checking up on him? If so that's all got to stop.
Second, he told you he wants to work on the M? Has he done anything towards that or just talked about it? If he really does, then it's time to present him with some boundaries. Full access to his phone and email for one, disclosing to you where he is and what he's doing throughout the day for another. He needs to understand that he has ruined the trust and HE needs to work hard at regaining YOUR trust.
Now if he doesn't want to work on the M, then you can't set boundaries. You need to find out if he's serious or not. I don't think he is.
