How to help aggressive overweight dog

My dog Charlie who I’ve had for years, has gone through years of abuse by my mother. Now that I have him and he’s in a safe place now, he’s incredible hard to deal with. As much as I love him I don’t know what to do and I need advice because I want to help him get better. My dog is a retriever and he’s currently overweight, 95 pounds to be exact. He can barely walk and I frequently have to help him get up, however he hates it when people touch him (sometimes). He likes being pet but sometimes he will abruptly snap and try to bite you, he’s bitten many people in my family and I’m not sure what to do. He’s also food aggressive and cannot be approached while he’s eating or hand fed. He also is heavily matted and incredible dirty but he doesn’t like being given baths and can’t hop in the bathtub either because of how overweight he is. What can I do to help him?