A cat that abused and that old (it looks older than a couple of years to me by the teeth and size) will probably never be able to trust again.
Ears? What ears? I can imagine all sorts of ways a cat can lose their ears. One of my ex in-laws had a cat called NoEars because they froze one winter and fell off.
A cat I rescued from the neighbors abusive children (one child held the front legs and the other the back legs and they would swing him!!!!) had no whiskers and healed scissor clip marks on his ears where they snipped at him. 'Otto' came across the street to me when they locked him out while they went on a 2 week vacation. I fed him, took him to the vet, and when they came home and wanted him back, I said NO.
: They didn't protest too much, and they went out and got a dog that I felt sorry for.
I kept Otto for years, and he had a happy home.