Damn...wish I knew what to say. All I really stress is RECON.
Hire a PD to go snoopin. See what he turns up. In the meantime, start setting up the battlements. Everything and anything that can be used to your advantage must be looked over and tested for integrity. Do this as low-key as possible, and prepare for battle.
If the PD finds out she was cheating, give her a chance to come straight. Don't tell her that you hired a PD to find it out, just be up front and ask her. Tell her that you know something...and that you'd like to hear it from her mouth.
If she refuses, then all hope is more than likely lost. Lock up your heart (for the moment) and become cold and professional. It's gonna be hard, but if you be Mr. nice guy, you're more than likely to gonna get rail-roaded in the end.
Kick her ass out to the curb and change the locks. As soon as that's done, get all the paperwork for the divorce you were supposed to be working on (remember setting up the battlements?) finalized and signed...and SERVED. Be sure to include a restraining order and an order that freezes all jointly-held assets.
Take all the info you have, and raze everything to the ground. Don't allow yourself to feel remorse...that will be your Achille's heel. Distance yourself and remain professional through it all. It'll be hard, but ultimately beneficial in the end (in terms of the legal aspect).
Best of luck, man...it's gonna be a hard road. It's gonna be an all-around rough time, but in the end...
"this too, shall pass."