I think those things are extremely personal. Would you rather him not have this guy as a friend, I know it to be yes. Is it so important that you are going to forbid him? That is up to you. And I believe the question you are trying to figure out, if I lay all of this on him, will it be a deal breaker or so controlling that he goes off somewhere in the near future and hides another affair from you to a woman that is cool with whatever he does.
I am sorry I do not have answers to any of this, some here will surely give you some, but I think it is within you and only you that the answers lie.
