Sit tight...she may be moving...and out of state would be great...but you need to see what is really going to happen...
I know it is hard to think that he would see her...like when I found the emails to/from OW and H was asking if he could call and talk to her on the phone...it never happened but if it had he is still here...bottom line they didn't pick things back up...
I do know it takes time to get over someone you have been intimate with...and sometimes this revisiting is to reassure they have and are getting better...if he is being nice to you...and making future goals...just relax...I know you don't want him to see her but you can't control that...if he isn't sleeping with her...or trying to create a R with her you need to let it alone...
I know he broke the "promise"...so did my H...but bigger picture...promise or not...he is still home and she is out of his life...it is a long process....both for you to get trust back and for him to let go of his emotional attachments...
he loves you and wants you happy...just a thought...if you could hold it together and not get into one your "beat the dead horse" discussions...is next time he makes a comment like this...just say I would be happiest if you weren't in contact with OW...then just SHUT UP!!!...even if he asks you what you mean...just say you mean exactly that...and that you don't want to talk about it...that is just what would make you truly happy...so now he knows...