What should you do if he tries to come back? Sell the house and move! Find a new city -- a new state would be even better. Toss your old email addresses, get a new cellphone provider, ban him from your social networking sites, lose all of his contact information and start over. Seriously, a clean break is the best and healthiest thing you could do for either one of you. Right now, you're just obsessing.
And get rid of his stuff! You're not running a U-Store-It out of your house.