Need Help to stop child from hitting me

I tried calling the police that ended in a horrible phone conversation claiming the police were not there to coparent. I was informed that if they came out I would be the one in trouble, I should either learn to parent my kids or send them back to fostercare. ANother time in public I had the police called to intervene with a dogooder screaming I was abusing my child. I had to hold her in a restraint on the floor to protect myself and other children. The officers that came out were fantastic and once I showed them the letter I carry from their therapist they competely understood.My son is violent and does a run up and kick me thing that is knows will get him to be held. I swear that is is goal when he is feeling out of control.