On the other hand, counselling could work – but only if he would agree to actually follow the counsellor’s recommendations. The only question is how to get him to do that. i.e. – 1) to agree to counselling, . . .
TT,
First of all, I think your stargazing stuff is WAY cool!
Regarding the above quote, you don't "get" people to "do something." That an ULTIMATUM, and it's controlling. You can only let them know what YOUR boundaries are.
A simple example would be to say "I forbid you to see this other woman!" (ULTIMATUM)
Instead, you should say (if this is indeed true, which is why I wanted you to do some soul-searching about what your core values are): "I cannot remain in a marriage where my husband is still having contact with someone with whom he's had an affair" (or whatever). That's a BOUNDARY.