Cat needs amputation immediately

Will you please help my cat?

Kitler is 7 yo, 6 kgs 4 months ago he was hit by a car and lost sense in one of his paws. He shuffled his leg and it caused him major injuries. The vet said even with surgery, meds and rehabilitation there is only 40% chance the nerves will work again. But we agreed to do so. Had one surgery, they put into him something inside to stabilize it.

For a while he should have been lying and not moving, loose weight, take meds, but how can you stop the cat from walking? Every time someone opened the front door, he somehow sneaked out and came back with his paw even more damaged, jumping everything and slowly learned to walk on 3 legs, only supporting on the sick one.

...in the end he needs amputation asap because the screws inside prosthetic loosened and broke so now part of it is sticking out of the skin.

The vet said it is only option :(
The problem is I spent almost 3000$ on meds, vet, rehab, etc. Basically all my money went for nothing, I have nothing left and the cost of the surgery is more than 800$ when I live + control visits, meds and other unexpected stuff.
I can’t bear to watch him so gloomy, depressed and in pain, especially when the spring is here I want him to go outside for a bit 3-legged but happier and healthier.
So please, help me heal my cat and please donate.
Thank you in advance!
Anna & Kitler