Spanking Babies: A Form of Discipline

Under no circumstance should anyone, Muslim or not, hit a baby. Babies cry a lot because that is their only way of communicating their needs. You and your husband should check to see why the baby is crying. Maybe he is crying because he is hungry, tired, needs to be changed, bored, has gas, or wants a change of scenery. Babies communicate to their parents, and if the parents are attentive they can usually figure out what is wrong. Has the baby been sick lately? Check with your doctor to rule out any physical problems.
At this age, babies want to interact more with loved ones and need physical contact that is positive. Encourage your husband to play with his son. Suggest they go to the park in the stroller or have your husband feed him. If your husband spends time with your son during quite times, when both are relaxed and not stressed out, he might enjoy parenting much more.
If your husband gets angry and takes it out on the baby, maybe counseling is in order to help deal with his anger. Parenting should be a shared event between husband and wife. Sit down together with your husband, when your son is sleeping, and discuss ways of caring for your son. If your marriage is strong and you are communicating with each other this will benefit your son in the long run.
This question of whether or not to discipline a baby does not rise to the level of getting a divorce. Divorce is always a last resort in Islam.