OP, I wish I could give you a hug. I am the author of this thread from 2012:
https://www.dcurbanmom.com/jforum/posts/list/268691.page
My son is now in 7th grade and he is so calm and sweet and kind. He can't remember any of his crazy behavior from kindergarten and preschool.
My son was hitting kids every day in school. He also tore up art projects and threw blocks at kids. People also asked me what was going on at home to cause this. Parents looked at me as though I was the mom of a serial killer.
My son completely outgrew the behavior by first grade. He is a very anxious child and the anxiety now manifests in a different way. Of course, as a 12-year-old, he can express how he is feeling and we can work together on his anxiety.
Perhaps you should find a new preschool or maybe the teachers can work with you to manage the situation. My son had a lovely K teacher. She let him sit under her desk with a blanket thrown over it to calm him down. It could take some out-of-the box thinking like that to help.
Anyway, I know you are a good parent and you are doing your best. I promise that it will get better and you and your son will have a good laugh about it when he is in 7th grade!