He gave the OP his password, and she told him upfront that she a) distrusts him and b) would likely snoop. I am not seeing a breach of trust. It is not like she was standing over his shoulder or holding a compact and perfecting the angle to watch him enter it.
I will not pretend to understand why he gave her the password. Maybe he wanted to get "caught." OP, does he have a history of cheating in his past relationships? His behaviour does not correlate to what an open person might do. Very odd behaviour. What if he had slept with one or more of those women, omitted it/failed to mention it at all, had unprotected sex, and passed something on to you? That is where my mind takes it. Shit always starts with one little omission, and it can snowball with the quickness.
You have the proof, but what are you going to do with it? I am trying to figure out if this relationship is even worth having when he continues to lie to you and removes another level of your trust every time you ask a question.
Ry - Me. Panromantic demisexual with a history of polyamorist tendencies. Married to...
Matt (Hubby) - The once distant stranger that I complement beautifully. DH of 12 years and father of our (3.5) children.