I strongly, strongly support marriage and relationships, and I can understand your husband's concerns. Please don't leave him for this Dom. It might be that you need to leave him because you can't express a core part of yourself, but that's very different.

Can you possibly express this part of yourself in the sacrifice of giving up your Dom? Your husband has "banned" you from contacting him, I think you said. Can you turn this ban into a submissive act? Can giving up acting on the submission be a submission to your husband?

I'm so sorry for what you are feeling, but I agree with your analysis. Fantasies can be overwhelming, but your marriage is a very precious reality.