I may sound like Captain Obvious over here, but have you actually tried addressing his 2 contrasting opinions of you with him directly?

That's the first thing I would do...
Ask why he says one thing to my face and the opposite behind my back.

Communication is key...

We can only speculate alongside you, we can't say why he's being 2 faced, only he can answer that.

Maybe he was fine with the the setup initially, and is too much of a coward to tell you that's no longer the case so he vents to friends or his daughter. Maybe he has no backbone and is just agreeing with their views of you to be accepted. Maybe he's just an insincere 2 faced prick...

The list of maybes go on and on.

I suggest you speak to him, and yes, snooping is never a good thing, but maybe if you can reconcile what he says to you with what he says about you, then you'll stop looking for truths in his private communication with others.

I'm sorry you're in this predicament, I would be confused and hurt too.