Should i just call him & get it over and done with?

I would have your son call him. Do not tell your son what to say over the phone. Let him talk to him whatever he wants to talk about. If he wants to see his Dad he will tell him. Don't force your son to call him let him bring up the subject. There really is nothing you can do to have your ex take an interest in his child. He is a dead beat Father who doesn't deserve having a son in his life. You on the other hand can be the best Mommy you can be. I know your heart hurts for your son however you have no control over the situation. If he isn't paying child support take him to court. It is up to your ex if he wants his son in his life or not. Your son will find out sooner or later that his Dad is a loser but he will always know that his Mom has always stuck by his side and did the best she could to raise him.