Allow yourself to go w/the anger. Embrace it and let it run its course. It is natural to go through as you have been the one doing all the work to save your M, so you have naturally built up some resentments.
There is also the part of resenting the actions of XW which caused you to lose your M, time w/your D and now your house. It is natural to feel, but be sure to find a way to displace the anger instead of the intended target of XW. She has no right to your feelings anymore and thus, you shouldn't let her inside to take a look around.
However, I do understand why you would want to apologize, as I've wanted to do the same thing myself. The problem is if you apologize, XW won't process it as she should. If she continues to have discussions w/you about her remorse, then you can say, "I'm sorry it happened too b/c it wasn't what I wanted at all" (or something of the like), but you don't owe her an apology.
Selling the house is tough and the market makes it even tougher. I wish you very well in getting a fair price that is good for you out of any sale.
