SG. I am sorry to say, but I am with Puppy that there is likely an EA. He probably wants to make sure you are in the picture in case it doesn't work out. He is testing the waters (so to speak).
How was your M a few months before the bomb? Were you having problems? Was he distant? Have you ever had major problems in your marriage? What were they?
By the way, I would normally tell you to limit what you say to the family. But since he is living with your parents, I guess that isn't as important. However, I do find it odd that he accepted that proposal. Has he ever seen an IC or a psych? Does his family have a history of depression?
I am not sure you need to go dark. But don't answer every random thing with an immediate response. When you do respond, be friendly, confident, and happy. Do not make him your focus right now. Your focus should be on yourself and the children. By the way, what are their ages?