Well, I think you're about to make a very grave mistake, but I'll tell you why. First, my prediction is kind of like the Mayor of Galveston giving mandatory evacuation orders - sure, things might work out fine, but the odds are bad and either you think things through or you foolishly go with your emotions du jour.
So first, with the house. The problem with the loan is that it may end up making things WORSE between you by causing resentment on one side, the other, or both sides. Finances are already a tough subject between people who are happily married; they're gasoline on fire between divorced people. Usually. The Boston area isn't exactly a spot for screaming deals, nor is it known for its low property taxes. XW may have the best of intentions in paying you back, but things creep up and nothing worse than property taxes.
This is why there are companies out there that specialize in harmonizing loans between family members; they keep things professional so it doesn't damage the relationship. The easiest thing you can do is not get involved, but if you do, I'd highly recommend one of these services. That way resentment doesn't build. After all, how will you feel if you find out XW and friend are sleeping together? Or let's say you meet someone and in a couple of years you want to get a place but XW still owes you most of the money?
You say she's worth the risk and the pain, but that clearly indicates that you're focused on winning her back. But the choice to divorce was yours. You need to own that decision. You chose that route for a reason, and it sounds to me like there are some major unresolved issues within yourself since you switched from that decision to your present state. Anyway, you can't make these kinds of decisions focused on winning her back. You need to focus on yourself and making yourself a better person who goes after the things they want in their own life. You can't focus on her as a way to make your life whole. If by refinding yourself, you win her back, great!
Sorry, I know this is a long post. But her response regarding the friend isn't exactly encouraging. My W had an A that I knew about, so it was a little different for me. But reading "Not Just Friends" by Dr. Shirley Glass really helped me see how easily confiding in a friend can become a slippery slope towards an A or R. That said, your W isn't having an A since you pursued the D, but she could easily be sliding towards a R, or already be in one, whether emotional, physical, or both. I think I'd agree with your friends - you're on a course that will intensify the pain.
Focus first on yourself and the friendship between you and W. Friends don't always say yes. Friends don't help each other buy houses (usually). Friends are simply important people that are there to support and listen when needed, do things together, make each other feel good with no strings attached.
I know the pain. We all do here. Some have been going through it for a long, long time, so I feel lucky to have only been going through it for a year. It gets better in time, though there will probably always be a hole. But you only have control over yourself, so that's where your focus should be. You shouldn't play games with ex, but neither should you be focusing so intently on winning her back. If you've told her you've made mistakes, she's heard it. Now she needs to SEE how you've changed. And even if she does see, it's going to take a long time, and she may decide too much damage was done. So focus on yourself and take the lessons you've learned to improve your understanding of making any future relationship work.
