This is more than a sex problem, he has a paraphillia, several most likely.
He is heading straight towards a place on the offenders register.
He will keep pushing and pushing those boundaries until he gets caught doing something he can't talk his way out of.
So far you have accepted everything else, more or less, he is looking to you to share his high.
Get off the train now, before you wind up finding arrestable material on your computer.

When he stepped in that room he stepped over the line.