I feel I'm at a crossroads with my 1year old cat. I am not sure to continue to do everything in my power to help him (which is getting very expensive) or say enough is enough.

[background] I adopted him as a kitten from the humane society and he had some respiratory issues. Fine, okay, it went away. Now a year later for his checkup we start to notice issues.

Last month he has a fever, lethargic, doesn't eat much, runny nose. 
He's prescribed antibiotics. They don't work.
fast forward two weeks...He's stayed a week in the vets clinic. They don't know what wrong with him. They run tests.

now he just got a feeding tube and they want to send him to a specialist two hours away. Still not sure what's wrong, might have better resources at this other clinic.

i work full time but don't get paid a lot and still have other bills. plus I'm worried about the mental toll this is taking.

but for now I'm financially / emotionally scraping by.

Hes my best friend. I love him so much. But am I just prolonging the inevitable? Then again he is only a year old. I'm so lost, tired, confused, lonely scared. I don't know what to do.