This sounds very similar to my ordeal. I have gone NC as possible with kids involved and have basically avoided even seeing her. She has been openly dating others through AM and other sites. I held out for months trying to fix things and DB as best I could. I finally had enough when she started being cold to the kids. I have since been reconnecting with old friends ( male and female) and keeping busy as possible. It has helped me tremendously. I have to agree with the others advice to cut her off. Let the lease end and let her figure out what being an adult is about.
M: 39 W:38 D: 11 S: 7 T: 18 M:13 I suspect problem: 8/15 ILYB: 9/15 Never quit on love I ask her to leave:10/15