Wow FFH. You are strong and have come a very long way from where you once were. This happened to a friend of mine and his ex would come over to his house crying hysterically on the front porch wanting to get back together. Eventually they did get back together and they say their relationship is better than ever, but I know that he still questions himself sometimes.
Not sure what I would do at this point myself if W wanted back. All the trust and most of the love is gone now. Still starting over will be difficult too. I haven't had a "sandwich" in a long time and I do miss the touch of a woman. It will be hard to decide IF it ever happens. I have worked very hard to get where I am, but the road ahead looks pretty tough for a while yet, at least in terms of the house and money.
Think long and hard FFH. She would need to be very repentant for me to take her back in your sitch. I don't think she is there yet. Maybe never will be.