If money is a problem, then see if there is a vet school nearby. Sounds
like a difficult problem so they might treat for free. The problem here
is the possible incompetence of the students and even the professors
themselves - so ask questions. And remember all those bad graduated
vets learn their inabilities somewhere.

When I had a cat with an eye problem, took her to the Penn vet school,
probably the best in the country or so they think. Fortunately they had
a visiting professor from Boston who correctly diagnosed the cat's
problem. I kept telling the idiot students that she was blind in one
eye, duh. Still difficult to comprehend the incompetence until I saw
people doctors. Must be something in the water. You can also ask. A big
vet clinic I know, someone could not pay but wanted care, they let her
pay off an entire operation, took a year, a dollar or two per week, but
she paid it off. So just explain your situation and see if they offer
help and let you pay as you can afford, even a dollar or two at a time.