Haven't commented on your sitch but I have been reading, especially since you & I are close in age compared to many others here.
This jumped out at me:
"So, she believes my s is in escape mode, is returning home to relive old fantasies, and very interestingly, she said emotionally, s is still 15 years old(which is the age when her stepfather started to abuse her). She is acting in a very adolescent way and is in a crisis situation."
My W reconnected with an old HS boyfriend through Facebook about a year ago. Had an EA, Dropped the bomb in March, moved out in August and invited him and his mother to move 1700 miles across the country and in with her.
Her HS relationship with him occurred at the same time she was abandoned by her mother and stepfather.
Like your W, my W is still an emotional teenager, and seems to be trying to relive old fantasies. I became the boring predictable husband; the OM is new and exciting.
You and I, and so many other husbands and wives on this forum, became complacent and probably took our spouses and marriages for granted. Honesty and open communication from, and with, our spouses might have defused our situations, but really, who knows?
Keep looking forward.
H 56 W 48 D27,S21 SS25 SS22 Severely autistic M(#2 for both) 9 1/2 yrs. "I've never loved you" 3/7/2011 Separated 8/7/2011 BITS