Here's my take: What seems clear is that he wants to have it both ways. He wants to be with you and have a family and a "normal" life. And, there is something about the OW that he is finding very hard to leave. I'd bet that that when he says he loves you, he means it, and that, even if you did nothing, he would eventually return to you.
The question then becomes how to accelerate the process, so that he returns before you become so fed up with it all, that you throw in the towel. I think I'm with lostlove here. You need to lovingly detach. That doesn't mean you threaten divorce, just that you let him know that you are ready to move on with or without him. Give him some notion that he may be losing you, and that he needs to act quickly, or the decision may be taken out of his hands. Don't be obvious about it, or throw it in his face, but it wouldn't hurt for him to think that you might be open to dating other men. Be intentionally vague about what you've been doing (and with whom!). Let him do the wondering for a change.
I know that your situation right now must be completely maddening and frustrating - to be so tantalizingly close to a real breakthrough, to be right on the cusp of success, and to not have it happen. You probably fear that anything you do differently may have the opposite effect of what it is intended to do, since your H has already slowly been moving in the right direction. But in reading these threads, there have been so many success stories using the "lovingly detach" approach, there really is very little risk.
Think of it this way. Right now, your H knows that he has 3 options: leave you, come back home, or stay with the OW while giving you "maybes" and "somedays". You can lovingly, and in a way that he doesn't even know it, take away that 3rd option.
