hi tish,
i am a Christian too. Personally i would maybe check a few things out:
1. who is babysitting him? do they hit him a lot?
2. is he around other children in some other environment who are hitting? he is learning this from somewhere's.
3. is he being allowed to get away with more than your other child because he is the youngest? they will see how far they can go.
also he may need more nap time and absolutely no sugar. not even juices without them being really watered down. that will give him a mood swing.
it seems like he is trying to see who is going to be the boss in the house and its a power play. be firm and clear with him about the repercussions of his behavior. it will be time out when he is bad.
hope this works. also pray over your home. dedicate each room to the Lord and put a cross in the 4 corners of the property. anoint each window and doorway with olive oil while dedicating it to the Lord. sometimes when you move into a new place their is some spiritual residue left behind and children will sense it. pray for peace in your home. let me know how it goes. blessings, Pastor L.