Ummm, yeah - I'm pretty sure he didn't get a secret second cell phone just so he could prank you. He's using it to communicate with SOME OW, whether it's still the old school girlfriend or another.
As for the house - yes, keeping a clean house is one thing you can fix. You should do so. But also remember, if he wants out, he'll just pick something else about you to put the blame on, so don't twist yourself into a knot. Fix the things that are legitimate complaints, and ignore the crazy stuff.
