Hi Broke (and sorry MB for the hijack!), I don't think that you contacting OW's H has accelerated anything. The way I see it is that you hurt your H in his pride because he could think he could have the best of both worlds, but you torpedoing his plans left him to contemplate his actions! Something WAS would not to deal with. Now he has to face OW's H and if he told OW that he would file once her H found out he really couldn't back out, could he?
I have been separated with STBXH for a year and he still hasn't filed, despite introducing OW to his eldest daughter & our girls knowing about her. Our kids still haven't met her! So I think that your H didn't want to lose face in front of OW!
As far as I can see it's all about pride. Hang in there Broke