I don't really know what to say. Lucia, you and your husband seem very unhappy together to me. Is that right?
I think you're wondering if his behaviour will change if you agree to a polyamorous relationship. I don't know if it will. But his behaviour to your seems disrespectful and mean, and I don't know if adding another woman into your relationship will make him nicer. I'm just guessing, but I don't think it will.