Re-read what you wrote: you scream and yell .. 5yr old screams and wails... you spank... he hits ...

Child is simply doing what parent is doing. If you want child to act right, then you have to act right. No matter how frustrated you get with child remember this- negative action causes another negative action. Instead of so much hitting, screaming and yelling how about trying calm voices and lots of hugging. Children learn by example. All of you are probably angry over the divorce and splitting up of family this is probably fueling everyone's actions. Did you get counseling during or after the divorce? Everyone needs counseling going through breakups. Might also help the kids. It also helps kids when you explain exactly why they should do a certain thing or not do it. Explaining why and leading by example are positive ways of parenting.