Well done Chicory! When my xah made statements like that I just did not say anything. I get entangled when I start to talk. My counselor at the time also suggested that I could come up with some 'canned' responses to some of the various baiting lines he'd repeatedly use. So in your case "Bummer." or "I have faith that you can figure that out." or "Yep, sounds like you have a problem." or some such thing. Something automatic and that can be said without sarcasm, pity, etc.
Hang tough! He'll likely pull out all the stops. I found that the slogans and one liners I read here really did help me keep my perspective and resolve during those times. I had some that were truely inspiring and some that kind of made me laugh - depending on what I needed at the time.