Well, first off, I don't see how you could learn much (re: your T's idea of "using him as an experiment") by trying to relate to someone who has such serious issues and who is likely only going to make you feel worse in the end. I would be weary of anyone who lies that much; you know you will never be able to trust him. T's advice makes sense, if this were a stable, balanced relationship, but it doesn't sound like he has the same things to offer you that you do to him. As for checking his email, I think you are only trying to protect yourself, so I would not feel too badly about it. It doesn't sound like you would ever do the same thing were the relationship (however you wish to define it) functional and healthy!

I know what you mean by "at least he is getting you out." I did the same thing over this past summer with someone I used to see about 15 years ago, in my early 20s. After a few months I realized I was happier by myself than spending time with someone so dysfunctional (not that I am all that awesomely functional...I am depressed and anxious; however, I do not treat people poorly, as he was doing to me). I was glad when I stopped seeing him...I felt much less anxious. I wasn't getting enough from spending time with him to balance out the negatives, if that makes sense.

Good luck in dealing with this situation, I wish you the best!!