I’m sure the tutoring helped your son. What didn’t help was purposely tanking later tests. He isn’t set if the ACT people rescind his score, so you need to talk to the college.
There’s a thread about ACT cheating accusations on CC right now. I don’t think they’ve reinstated anyone’s score. Your son may have to retest to validate his score. If the college won’t take it, he may have to take a gap year and apply with new test scores.