According to the vet, the surgery will completely fix the problem, and he will have no lasting ill effects.
Some vets use Care Credit. Might be an option?
That is a worm on the line. I am a nurse.
Can you get a loan? Credit Unions will loan you the amount you have on deposit. That may make it easier financially.
In that case, and since you are emotionally attached to your cat, see if your vet will take installment payments for the treatment... that way you can save your cat and still be able to take care of yourself.
If the surgery would not completely fix the problem but would have only put off the inevitable, I would have advised euthanizing the cat.
Since you are the only one here totally familiar with the situation, we can't make up your mind for you. But I wish you and your cat all the best!