How do I correct this behavior

My son is 2.5 and will absolutely not listen too me or dad, In the past I would not allow dad too discipline him or correct him because in my eyes he was a baby & still very much is I always found dads tone of voice too harsh. It’s too the point where my son doesn’t even respond to being corrected he takes himself out of time out, he’ll pop you back if you pop him & he’ll constantly tell us no when given and order to stop doing something he knows he’s not allowed too do. I try taking his iPad he goes back & gets them. I dread taking him out in public because I already know a tantrum is waiting for us it’s embarrassing. I feel so bad yelling at him or disciplining him I’m scared it’s too late. & now dad won’t intervene at all when I need him for reinforcement