I empathise with you and am sorry that you are in such a painful situation.
I think your husband is a mean prick and needs to go. from what you've written, I have no hope that he can or even WANTS to change. Stop enabling this abusive pig-man, stop letting him demean and devalue you.
How old is your son, the one with the allerdgies? i think no matter his age, that if you sat him down and told him the truth, reasoned with him, he would be ok with finding a good home for his dog. It will still hurt you both, but it is the loving thing to do, for your boy and the dog.
Congrats on writing your book, that is really an acomplishment.
The biggest emotion you may be feeling is fear, or a feeling of being stuck in a situation. Do not let fear keep you from action, you will regret that in later life.
If you do decide to leave your husband -he sounds like the mean sort that will torment you relelntlessly- DO NOT THREATEN him or warn him of your intending actions. Do not confide in the children your intentions, but you might gently question them about how they feel home life is or however this issue manifests in their life.
Seek legal cousel, and when you act, act first.
You will likly loose your current home, and that is sad and scary; but it is just a house. You and your children are more important. You can buy another house.
I'm sorry if my words are too blunt for you, I've seen this sort of thing in my personal life. My sister is in a strange relationship with a man who physically beats her and assaults her. He has injured her right hand with a knife and damaged her nerve. She is in nursing school and can't use her damn hand. Her kids live with their father, but her oldest lives with our mother and myself. She is a toxic person who we all have had to distance ourselves from.
Painful choices can hurt now and are scary to go through, but the investment in the future is worth it.
What ever you do choose, best of luck to you.