What a tough decision, glad I am not in your shoes right now! I say, follow your heart, only you can really know what is right. He is a cute little guy and it sounds like you want to keep him. If you are sure of the breed mix he is, at least you know what traits you are going to deal with.
I think he looks like an interesting little character and if he fits into your home with the other critters...sounds like a keeper. Good luck and keep us posted.
