Forget the checking out of things, the writings on the wall.
open one of your own under a fake name in the same city see what you can find out...
You need to go into the profile he has created and more times than not, it will have a "profile created date." Good luck and hope it turns out for the better for you.
That is not evidence, that code only suggest a link from an ad to the site. I think the best thing to do from here is talk to your partner and try to sort it out the good old fashioned way. If your partner gets all defencive or does not want to discuss your genuine concerns, then rethink your position.