@AbbyD,
I know this doesn't answer your question totally. But, when you allow someone to take from you constantly, they will always continue to take as they know that they can.
3 years apart and yet, still together "hanging out", yet he has clearly told you, you are FWB's, nothing more. And, then he ensures he continues to have you where he wants by letting you know clearly, that you can not date anyone else.
My question to you is, what is it you love about him? Because, what ever it is, it's there somewhere else and you won't be disrespected or disrespect yourself any further.
I don't think most men sleeping with someone likes to loose. But does that mean that you just "hang about" for another 10 years for nothing?