Not sure when the opportunity will present itself, mdu (but I'm sure it will) . . . but I think your next huge "test" as it were with him will be when something highly controversial/upsettting DOES come up, and how you react to it.
If you think about it, you've avoided "going off" by pretty much avoiding the hot topics -- keeping it light and airy, as it were. At some point (and I'm NOT saying to go looking for it, but just let it happen naturally) an upsetting topic is going to come up -- like OW contact at his office or something -- and how you handle THAT, I think, it going to be a great opportunity for you to show your husband that he can trust you to work thru the difficult reconciliation phase with him.
I would just keep doing what you're doing, and be ready for that day -- practice it in your head. Calmly stating a boundary, but doing so without going off on him.
