Since my dominance is heavily oriented to sadism, I can appreciate this man's position: I know how exciting it is to have a sub who really isn't enjoying what one does but endures it anyway. But it's a delicate job not to push the sub so far that it becomes abusive, and it seems to me, as to the other posters here, that he's crossing the line.

Whether you call yourself a Dom or a sadist, you still can't just keep pushing someone where they really don't want to go and telling them they'll learn to love it. I've done that occasionally for one or two sessions to get someone through a limit, but if it hasn't worked quickly I've backed off and accepted that the limit isn't breakable.

If you haven't discovered a way to handle this yet, I doubt if you're going to, and he should accept that, and either find another outlet for these needs or release you and find someone he can use the way he wants.