I agree with Sam. This doesn't have to be all sorted out in advance. There is nothing wrong with going with the flow, which is what your STBXH wants to do. At some point you should indicate what you want out of a relationship and what some of your anticipated issues will be (ie trust, etc) so that he is aware of them, but it doesn't have to be yet. Let him take the initiative on that.
He isn't going to come back like a woman would...after talking things through. The only problem is that he will take you spending a lot of time with him as a "yes" to coming back. I would suggest spending a pleasant, low stress, low demand evening with him (and your S) and see what develops. If at some point he opens the door to reconciliation talk, that is the time I would choose to state what your hang-ups may be. Don't talk about what he needs to do or what actions he needs to take. Let him tell you himself without prompting. You control the situation now and you also have the breaks. If he starts talking about moving his stuff back in, just say, "Whoa. I didn't think we were at that point yet. I still have some issues trusting your motives and your commitment to trying again." If that is enough to scare him off then I guess he wasn't ready anyway.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
