Neurological and urinary issues

Hi everyone. I have a 4-year-old cat who came home 5 weeks ago in a terrible state. His tail was limp, his back legs were dragging on the floor, and he absolutely reeked of urine — basically, we went straight to the vet. After checking him over, the verdict was two displaced vertebrae and a haematoma on his belly. His bladder was also completely full. The vet thinks he's been hit 🥺. For the last 5 weeks, it’s been daily trips to the vet to have his bladder expressed. He’s on Xatral three times a day. Since Monday, he won't let the vet touch him anymore, so they can't empty his bladder. He goes to his litter tray and gets into position, but nothing comes out. The only time I see any urine is when he’s cleaning his bits; then a few squirts come out. He isn't allowed outside anymore. The vet has been clear with me from the start: if he can't manage to pee on his own, he’ll have to be put down. We’re trying to find solutions; she’s now suggesting neutering him and amputating his tail so he can go back outside freely, but she says that doesn't guarantee he'll start peeing on his own again. I just don't know what to do anymore. If anyone has ever been in this situation... Thank you.