handicapped pup in need

This dog isn't just a mans best friend, shes my baby boys best friend. she rides with us 95% of the time when we go out, and she sleeps at the foot of his crib to protect him at night. she is always there at the end of every meal to clean up after baby jackson. well 2 days ago we went to the grocery store for no more than 30 minutes, we left her outside on the leash sense it was a pretty day and she chewed right through it and got loose. she got hit by a car and the driver left her behind for us to find with no explanation. poor remmy couldnt even walk and she was even bleeding from her eyes. we got her inside and i tried to give her water and i tried to feed her and she was quivering in pain. i got her special blanket that shes had sense we brought her home and than i got on my phone and i found a 24/7 vet, and she has been in the vet sense that night. a few hours ago we got a call and i just got told that she has a torn knee ligament, and 2 broken legs. we have to somehow come up with $1,578 for her knee and $1,586$ for her legs. my family just wants her home with us, but we dont have the money to pay for her to get fixed.  we dont want to loose her, she is a part of our family... but we cant be selfish and make her suffer. it would mean the world to jackson, and us if we could get any type of help. and we would be so grateful for anything.