She is totally testing you IMHO, Atlas, and I believe she's pretty much been doing this since the separation. I have to say I feel like she's toying with you to some extent. I mean, asking you to have some beers and make a night of it, then backing out after you say yes? That seems kind of ruthless, to me. If I was in your shoes (and I know it's easy to say this), I would not accept things like that at this point. I think you need to take a stand. You said you don't want to go through this back and forth stuff with her anymore, but here you are once again. Maybe the next time she invites you to do something, tell her that you appreciate the offer, but it hurts you how she pulls you back and forth the way she does. Tell her that neither of you benefit from this, and that it isn't healthy for either of you to continue this way. Say that she needs to find herself -- figure out who she is and who she wants to be, and that until she can do this a full separation/divorce that is completely business-like in nature is what is best for you and your own emotional sanity.
I'm sure you can find your own words/ideas, but that is just what came to mind for me. It's time to really look inward and ask yourself what you really want and what is best for you. IMHO, your W has a lot of sorting out to do, and she's not going to be able to do it under these conditions. If you continue to enable her by always showing her you will be there for her and that she can fall back on you whenever she wants, I don't think it will good for either of you. I could be wrong, though -- it's just my opinion. I wish we could see what a DB coach would say, given the circumstances of your R over the last few months.
If you can continue dealing with W's swings as they are, then by all means continue doing so. I would just set up some boundaries w/ W for your own well being. I think she will be more likely to work on herself and get better if you do so.
Hope you're still getting better health-wise. Talk with you later.