Ok, I feel the need to say we've been kind of inundated lately with stories of cheating and unsafe practices. Most of them have nothing to do with D/s. Yes, that's an aspect of the OP's situation, so it makes sense to factor it in, but most doms wouldn't act like this and most subs wouldn't take it. And there *are* tons of classes, books, seminars, and web resources out there on how to be a good dom (ALL of which focus on safety, respect, and consent, OP!!!), but I don't see some sort of official licensure process as being a likelihood any time soon (though that would be interesting). It's just a matter of trust and common sense, the first of which has been broken (as happens to so many couples) and the second of which is being ignored (the suggestion to think about what you'd say to a friend in this situation is a really good one).
OP, please do look out for yourself -- he's made it clear that he doesn't have your best interests at heart.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.