Sounds like he may feel abandoned and unwanted. See if you can get him in for counseling. Ask your school for referrals.
I googled and found this place that says it is affordable Putnam Counseling Center
3430 Teays Valley Rd
Hurricane, WV 25526
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I also found a Church Angel Christian Counselors Directory for West Virginia and they had a listing for NEW HOPE CHRISTIAN COUNSELING ###-###-####
1208 6TH AVENUE, HUNTINGTON WV 25701
Spanking or whipping doesn't seem like a good idea, although I totally understand the frustration leading to it, because it tries to stop the behavior with the same exact type of behavior.
Also, it might be a good idea for you and your husband to each spend some time alone with each of your 3 children. Maybe at least once a month, you could spend time alone with each of your children and your husband could also. With your nephew, since he is older, maybe you could ask him what he would like to do. You and your husband could also take him to do something with you and the 3 yr old.
I hope things improve for you soon.