Help disciplining child

My son is too grown for his own good, he turns three in a couple days. I’ve never met a child like him and I don’t mean that in a good way. When I try to discipline him, I do try gentle parenting first — I tell him what he can and can not do with explanations, I repeat myself several times, and I do give spankings if I’m repeating myself over 10 times. He uses my words against me. “No talking back momma.” “I’m talking mom!” “It’s not your turn.” are a few examples of what I mean— this gets him in trouble with both mom and dad. He is used to being in daycare but recently got taken out in September. He hits himself or things when he’s frustrated and I do try to talk him through his anger, tell him to breathe, etc. My family has never met someone like my son who thinks he is grown. How can I go about this? My husband has never disciplined him but he is getting to the point because my son is just, in a sense, too grown. Help?

I would like to add that he did gain a baby brother in September so my patience and everything is horrible. We are really trying to figure it out because we don’t want to be traumatizing our children.