Pup, i don't know if I like the part about "when you're done with her we can talk"... It just makes it sound like she accepts an open marriage temporarilly...
I prefer something like "Etiher YOU are done with her, OR WE are done with YOU"
and I would call it an AFFAIR, not a relationship. NEVER use the word relationship to describe an affair, it dignifies it...
Would you describe a stalkers association with their target a "relationship?" Not likley...
I know technically it is, from one def is the term, but the term relationship has a common meaning for romantic involvement.
I don't consider an affair a romantic involvement anymore than I consider pornography art... its sleazy, hurtful, and destructive.
Use the word AFFAIR... and tell him you don't want to hear his explanations, tell him you have known him for x years and you can telll when he's full of $hit.