I really really need help!!?

I have a Border Collie and when he was a puppy he was a really good dog he never jumped on people,never begged,never jumped on the couch,and never bit as hard as he does now. Now he jumps on everyone and always pushes us over and it hurts really bad especially when you hit your head. He begs to if you don't give him any food he starts making a high pitched scream and lunging at you for food. Now he jumps on the couch when you sit down he body slams you really hard takes your whole hand in his mouth and bites down really really hard. I have tooth marks,scratches,and bruises from him. The reason why he does all of this is my grandma. Me and my Border Collie started to form a bond he would stick to my side and never leave me. My grandma is OBSESSED with having dogs like her. If they don't like her the most she DOES EVERYTHING to get them to like her the most. Every dog we got ended up being my grandma's dog it makes me cry every time. I finally got Milo and payed with for him with my own money.Once our bond started to form my grandma started to feed him lots and lots of human food. He started to beg. She would grab him by the paws and dance with him. She would make him jump on her by saying up up on me on me!! She would pat the couch and drag and him up there and she would let Milo bite her I told her that she needs to stop. She didn't though she thinks it's hilarious that he acts like this. I want to cry so much. I have tried everything to teach Milo to stop. When we got him as a puppy he would chew on us but never bit us. Yesterday she said "want to chew on me Miwo? huh mighty mo?" and she stuck her hand in his mouth and let him bite her and she just said "ouch miwo!" "not so harddd!" she even lets him put his paws on the kitchen counter when hes trying to get food off. Since shes started this Milo doesn't even care about me anymore he completely ignores me. I cry every night because of this I wanted a dog so bad but he ended up turning out to be a bad dog and to love my grandma the most now she says "come to mommy miwo!" it hurts alot. And please don't say it's your fault or it's unfair to blame your grandma! My whole family agrees with me my aunt said "she pretty much taught him how to be the bad dog he is today". I try everynight to get him to stop but it's really hard when my grandma keeps letting him do this stuff. I really need help I want Milo to quit and I defientally want my own dog:( I play with alot and teach him stuff and give him treats and brush him and love him so I don't get why he decided my grandma was more special?