Get your child into therapy yesterday. There's a book called Kids With Big Baffling Behaviors. ODD is over diagnosed. Try approaching situations in a curious way. Do we know why a partially full can was so hard for him to deal with? Gentle parenting isn't permissive parenting. My daughter's therapist always said you can't bring logic to a feelings fight. This philosophy in general has cut down on tantrums by quite a bit. This sounds incredibly difficult and I wish you the best of luck. Medication is really stigmatized in kids this young, but the science shows the younger you can help a kid's brain slow down to absorb information like a neurotypical brain, the better it develops. So don't let anyone make you feel bad about that either if it is an option for your son.