move on, i say!
Well, it's amazing the similarities in this story and my own. My advice would be to stay away, and move on best you can. I had a similar situation of chronic fantasies/masturbation of her with the guy she left me for at the start. He was a 6'2", younger, gym instructor, well off etc.
Then one day the reality hit me like a tonne of bricks as soon as i realized she won't be spending Christmas with me, as we "split" in mid November. I started to feel sick at the thought, built up the courage to ring her to see if we can try again, thinking, she was sobbing at home, thinking like me and of me...only to find out when i rang her, they were in a resort in Bali, with all his coupled friends and that they had planned the trip earlier in the year with all "their" friends.
Humiliated, i told family and friends we were just having some time apart, until my friends and sister saw her at out usual places, snuggled up with this "new" guy. 12 weeks later, my sister saw her again pregnant... to him...my sister never liked her...but did say her boobs had gone from E cups to G cups, and looked fantastic. So i had gone from jerking off, imagining her with this guy in hot sexual visions, to intimate loving embraces, laughing, cuddling, loving her amazing pregnant body and the feeling of nirvana i always felt inside her amazing pussy. Also doing the very dirty things to her that she loved so much....that i thought was our secret fun.
Once the depression came, so did the impotence and the extreme premature ejaculation problems, which at some level are still with me 4 years on.
So to be honest...the bit in your story where she left her wedding ring behind, to me is the signal that it has ended in her mind, as looking back i realised now, once she did that, she was never coming back...and for your mental, physical, financial and sexual health...i would move on if i were you...easier said than done.
I still struggle with it till this day, even with a new woman and child in my life...losing that women is something i know i will regret for the rest of my life. She was my soulmate without a doubt...but foolishly showed her my submissive, beta male side...eating creampies of others and my own, sub bi, strapon play, x-dressing, happily highlighting i always have needed to wear small condoms for her amusement etc. she will get better sex with other men ,especially hung alpha males...she did in the end and still does i guess?
Not a day goes by that i don't think of her and the amazing sex we had together.
Slinky