Rebel,
I get it. I don't have Obsessive Compulsive Disorder (OCD) and it would be very difficult for me not to read his searches if I had access to that type of information.
My concern for you is that having the information seems to cause you more anxiety and pain than not having it. I guess there is something in the saying, "Ignorance is bliss." 
I guess my point in my post about parents vs. other family members is it is very easy to say, "You should" when you are looking at things from an outsider's point of view, but very different when you are actually walking in those shoes.
I think it would be a good idea for you to have him change his password. Having it just seems to cause you so much pain. I am not sure how I would approach telling him, though.
I'm glad he is rebooting himself. Dreading something really is worse than the actual something.
