I have not responded to your post until today and I have not read all of you stich, but if I may add my 2 cents into this mix. I may have a unique perspective on your dilemma.
I think (PM) has a good idea. It seems to allow you time with WM and W without making into something too heavy. It sounds like a natural progression and the normal thing to do, even with a friend. Give some serious thought about (PM’s) plan.
My stich as come full circle and the W and I are back on track. (See WAS, My Final Post, Very Scared 54 for the story). It is ironic that our U-turn back began with a lunch date with W on her birthday. It was a short 1 and a half meal in a public restaurant of her choosing. I was very nervous about the meeting, but we had not seen each other for about 3 months, 4 days, 6 hours, and 12 minutes. This meeting gave me a little time to show her that I had made some changes. It gave me an opportunity to give her a small gift. Do some flattering, tell a few joke or funny stories, and do some very light flirting. We were able to talk about the kids and people we knew. We caught up on what we had been doing since we were separated. NO RELATIONSHIP TALK!!! The more we talked the more relaxed I became. And the gift, the gift was something relatively small and inexpensive and in my case it was silly. The gift related to something I knew she would like that no one else would know about.
I did not totally appreciate the importance of the meeting at the time. But, little did I know, that this short 1 ½ hour lunch would turn into the first step back. NOW! IT WAS THE FIRST OF MANY STEPS. But looking back it was actually the key that unlocks the door. The door that was locked just a few hours before was now unlocked and ready to be opened when the time was right. We had to take a lot more steps before we actually came back together for any meaningful rebuilding of our R/M. But we have made it through the forest and into the clearing. The clearing of fresh air, blue skies, green grass and sweet cool water.
Like I said I do not know that much about your stich, but it sounds like there is an opportunity here and you should strongly consider taking the chance. It may not give you the key to the lock, but it may bring the key closer to your grasp.
Good luck to you on what ever you decide to do. Just remember, keep your eye on the ball, take a slow and steady swing and shoot for the green.