It sounds like this is a kid who is starving for affection from an older male. He may also be having some homosexual feelings (which many young boys do and grow out of....unless they have an older male to help them lock those feelings in).
If you really care about this boy, and it seems that you do, I would actually have a talk with the dad. I would tell the dad that 'feisty' really is clinging onto attention from you and that you are happy to be a friend to him, but you want to be able to impart the same values that the parents have to him.
Boys absolutely need men in their lives, other than their dads, who they can bond to, talk with and look up to as role models. My church encourages all Christians to look to those older and more mature as role models, in the hopes that those role models are ultimately looking to Jesus. I have been very fortunate to be a role model to the twins and to some of the other boys in the church, while many of their dads are role models to me.
You are not alone.