[YorkieMother]

First sorry that right now things are very overhelming.
I would say find a rescue and get him assessed as to even if he is fixable
I not seeing undersoicalization although I am sure it is a party of it. I am seeing a dog with serious mental health concerns and he was born that way.
Many of these guys are genetically aggressive and undersoicalization makes it worse.

You are not able to take on this level of hands on work that it will take to see if he can be turned around and honestly when is starts this young it usually can not but tha does not mean like my girl that he can not find someone that will do everything in thier power to hep him as they have the time and the health to do so.

I think if you ahd toe time that getting him assesed and a proper understanding of his concerns would help you feel better letting him try life some where else.

JL