Re: Sad and Angry
Whatever you do will be difficult. Think about which decision is best for you and your son, and for your mental health. Then make that decision. Try not to worry about the future, do what's best right now, because you're living in the "right now". We all learn to deal with losses. As an aspie myself, I can deal much better with loss than with constant anger, chaos and agitation.
Can you talk to your son? If so, acknowledge that you recognize he is furious with his father, and share your own feelings about the situation. Tell your son you may have to do something unpleasant to solve the situation, perhaps police, and you just wanted him to know ahead of time. Even ask him if he has ideas of how to solve the problem. If we are given a "heads up" in advance it gives us time to get used to the idea, so it doesn't scare/affect us as badly when it happens. Bring up the fact he will see his father less, and ask how he thinks he will deal with it. Aspies are generally way too smart, too early, but you can talk about things with them that you can't with most children.
When I got divorced, I discussed it a lot with my son. To let him know it wasn't his fault, kind of talked to him about how our lives would change, and told him he would live with me, but that I realized I forgot to ask him (at age 6) if he had a preference of who he lived with. He thought about it carefully and basically said he would miss both of us very much, but he would miss me most, so he would prefer to live with me. I never did anything to try to turn him against his dad, nor block his dad from coming to get him. He got to see for himself all the broken promises, and how he was never on his father's priority list, and how often his dad lied. Though I didn't think of my husband and me as "fighting", my son said he was glad he wasn't having to watch us fight anymore.
Good luck with these hard decisions, you're in a difficult situation.