You know, I think you've been more than patient with this behavior. There's something pathological in his continued involvement with her (are they laundering drug money, do you think?).
I know you said she doesn't speak English - so of course, you don't know what he's been telling her. If you're really at the point where you are willing to risk it all - then what about finding someone to translate a letter to her? Tell her all the things your H has been telling YOU, and that you realize he must be telling her something completely different. Maybe let the OW be the one to get pissed off at him?
Or - hire a P.I. and find out once and for all what's really going on. Or bug his office? Okay, I know I'm getting carried away here now, and we're not supposed to snoop - but H clearly isn't telling you the truth about anything that's going on in his life. For all you know, he's a bigamist, or he's taken out a huge life insurance policy on you and plans to poison you, or he's simply enjoying living a double life and is feeding the OW some line of BS about why he can't leave you, ... or the probable truth - he's just a huge weenie who can't bring himself to cut his ties with the OW.
Maybe you should just hire a P.I., find out everything, then bring a translator with you and sit down in the office with H and OW and tell them everything you know? I'd love to see your H squirm his way out of that one!
I know you've said you're financially okay without H, but I'm still worried that he has all these financial deals with OW that you know nothing about - I'd hate to see you get stuck with his debt.
Okay - I realize I'm venting about YOUR H - but it seems to me that there's never going to be real progress in your sitch until all these secrets are out in the open. I know that means risking it all - but it sounds like you might be getting close to that point?
What about this as a first step? Simply look over the bill, get a sitter for the evening, then go out with him and ask him what it all means. That's what a normal person would do in this sitch. You've been trying to let him work through all this stuff for so long, I think you're forgetting what a normal reaction is like!
Whatever you do - I'm sure sorry he's being such a jerk.