Do consider cancelling your Facebook account. Remove yourself from Facebook and similar sites entirely if you know staying away from your ex is going to be really tough for you. I know it sounds radical, but do you really need to know where the high school friends you haven't seen in umpteen million years got drunk last Saturday night?
Do use social media to advertise your singledom and meet new people. I'm a big advocate of online dating post-divorce. If you feel like advertising your single status online is somehow unfair or disrespectful to your ex, get over it. You're completely entitled to move on however you see fit, regardless of the circumstances of the demise of your relationship.
Do ignore posts you think are about you. Your ex, their friends and family may post things about some unnamed party you believe to be you. It may or may not be you. Even if you're 100% sure it's you, don't bother responding. You'll feel better taking the high road. Forgiveness is a virtue. Practicing it makes us happy.
Admit it. You know that if you want to feel better and move on with your life, surveilling your ex is not the way to go. Besides, de-friending is empowering.