Expect your child to test your limits - just as your husband did. He watched daddy get his way for years. And if daddy's anger took away from him, which it had to in a variety of ways, your son is angry with you at some level for not putting daddy in his place. You don't mention your husband's position in all this. I always tell my parents that it doesn't matter what they agree on - as long as they agree .
Consistency is very, very important.
Very, very destructive and emotionally very, very unsafe for your kid. I don't know of any books that specifically relate parental discipline to verbal abuse per se, but that's not a problem. Read it with your husband, or at least tell him about what you are learning. This is the best book I know. Emotional discipline puts too much pressure on your child to perform to make mom happy, or keep dad calm, etc.