Yes, get the divorce DONE and get your settlement money. You need to get your financial life figured out and that's an important piece of it.
Settling the financial aspects of the divorce (let's face it, you've been divorced in all but name only for quite some time) is an important step for you to finish. And it IN NO WAY prevents him from coming back IF he is really sincere, wants to do the work etc. You can even present it to him that way if you want - that maybe you'll get back together in the future, but for right now, you need the divorce done.
Odds are, things aren't working out with the OW - OR he simply isn't ready to pay up yet for the settlement. Don't feel like following through with the divorce is closing the door forever - plenty of people do remarry. IF he were totally sincere (which you doubt, I do too) - but IF he were, nothing is stopping him from stepping up to the plate and wooing you back AFTER a divorce.
