Disobedient 3 year old

My 3 year old stepson has just recently started throwing these insane tantrums. Like something I’ve never seen before. If he is ever told no or is told to do something he doesn’t want to do.

Ex: bedtime, he says no and then throws all his things, pulls the sheets off his bed, kicks, slams his headboard against walls, screams at the top of his lungs.

Last night he had a meltdown in hobby lobby for a toy, was told no due to his behavior prior. Wouldn’t allow us to buckle him into his car seat. Kicked and screamed, literally fist fought my husband. He pulls his own hair, hits himself when he’s mad.

I really am torn in what to do. At his mothers house he is neverrrrrr told no. She doesn’t force him to take naps, she said “if he doesn’t want to nap I don’t make him” WHAT HE IS 2, 3 NEXT WEEK. So this is really hard 😩 we let him scream it out a lot of the time but I have a 6 month old who is trying to sleep at night and his screaming stops that from happening