Do you realize that while what you're doing is a good thing, it's not enough? That puppy will suffer emotional consequences for lack of socialization (maybe even aggression. More likely severe separation anxiety and/or fear, and innapropriate behaviors), and it will suffer physical problems from not being able to exercise or play. What you're doing is great, and I'm glad you're doing it, but it is NOT ENOUGH. That puppy deserves far better, and you are the ONLY one who has the power and will to ensure that he lives a happy, healthy life. He will not have the run of the house when he's older because he will exhibit innapropriate behaviors (housebreaking issues, destructiveness, biting, etc.) from never having been socialized and trained. More likely he will end up in a shelter!
DO SOMETHING. Do whatever it takes to give this little guy a chance, including involving the authorities like JM said. If I can help you do the right thing in any way, let me know, please. I have a Yorkie myself, so to see any animal suffer--and especially a baby that looks just like my dog--breaks my heart. I will help you any way I can to get that dog a new home and the life he deserves, ok?