I am very sorry you are going thru this. when you say dating do you mean as in she is actually going out with these guys? like in meeting them somewhere or online?
For me when I had had my fill of the crap I was in and only when I had had it did I leave. no one can tell you when enough is enough.
talk to her. communication is the key here. maybe get some marriage counseling to try to save the marriage if that is what you both want. again I am very sorry.