He gave you the opening to bring up the issues regarding finances... It isn't pursuing when he made the first contact..
Just email him back and say something to the effect of..
"What are you going to do about the house payment being overdue? I am not going to pay your portion and would appreciate it if you would take care of your end without me having to tell you. I am not going to allow this to ruin my credit, so if you don't take care of your responsibility then I am going to take other action. If I don't hear back from you by Sunday night,then Monday morning I will contact the creditor (s)" to see what my options are and help them to deal with you directly.
