AHhh I'd definately believe your boy is all Yorkie
. I do not like the idea of leaving him in a crate all day
He needs to be around people and feel like he does not have to use fear aggression. That is what it's called . I think that getting him fixed will help settle him down , then it will be a lot easier to work with him.
Who can blame him for his fears around children after how he was treated? He needs to have positive experiences with kids/men/and other dogs. Then slowly build up his confidence and trust. there has been too many negative , bad experiences for your dog , which has made fearful and aggressive.