I am sorry you are going through this. Sounds like the troubles with the wife, resulted, in his needing to cut off all communication with you

Hard to say, whether it was or wasn't an emotional affair. Not all friendships, take away from marriages, so without understanding how or why, I cannot either say if he was just using you until things got better?

Did he explain, how and what made this an emotional affair? Was it mentioned through marital counseling?

Just because it ended, between you, doesn't necessarily mean that things are all rosey between, them, either.

Depends on the nature of their troubles?