I believe you when you say you don't want XH even as a friend. I believe you when you say your life is complete without him in it. Everything you say is correct. BUT, I still think you should wait those few days and send the simple text answer to his question. Only you can allow it to become an ongoing conversation. Just do it out of courtesy; the same as you would do a complete stranger. You don't have to be even friends, but if there is a chance of at least being not-enemies, I think you should grab it.
I don't know where this advice stands in the way of DB'ng. I'm not espousing that at the moment. That's over and done with for you. I just think you will be more at peace if you answer the question and then let it drop. JMHO!
