Rachel, id wait for someone more experienced to advice, but of course its a no!
Have you decided You are filing for D? Is he filing? Im 5 months in and d talk here and there, but i still havent seen the papers!
Please dont initiate any r talk with him, just boot him out and let him go, honestly he seems messed up and he will mess with your head!
I obv dont know his family, but be careful with his sister, i was very close with mil, but now our relationship is very limited and we only talk about kids. Its natural that his family will end up on his side or at least will try and keep things neutral.