How to get answers out of him subtly, without sounding like you dont trust him?

being a guy (not that i've ever done what he's supposedly doing) i can tell you that until his conscience gets to him he will never tell you what you want to know. I would ask him straight up, out of the blue, if you could see his phone and try to read his reaction. pretend you left yours at home when you go out or something. if your not to good with the reconnaissance, try considering not being with him. I can imagine being with someone you don't trust is hard and if it gets to be too much, tell him that he lost your trust and needs to gain it back. If he fights then leave. If he changes then be glad. Either way somethings got to give. Good luck