Cat may pass soon, how to make him comfortable?

Hey there, I am posting about my male cat Sonos. He is 2 years old. I am in the US. I am scheduling a vet appointment tomorrow for him, but appointments are far out and I am just feeling kind of hopeless at this point.

My cat is intact. He has been pacing around and yowling and stands in an odd way, kind of back part and legs alittle bit low to the ground. Hes eating all of his dry food, using the litter box, and drinking water as far as Ive seen. I havent seen him use the box much today, though. His stomach is round and firm. For more context, hes always been very vocal since a kitten. I recently rehomed anther cat I took in due to him also being intact, and attacking Sonos. Now, even though hes gone, Sonos walks around the house looking for him and fearful, whilen yowling. I cannot tell if hes in a dangerous situation or not, if its pain or hormnes, all I can do is pray I can get an appointment for this week.. I make 22,000 a year, and I am riddled with debt due to being young and careless, I regret everything. How can I make him as comfortable as possible incase he passes overnight?

Carecredit and debt is not an option and non profits are mostly not taking applications, I unfortunately am doomed to watch my pet pass. Its hard not to feel like a failure. I dont know what to do or how to feel.

TDLR: Cat has awkward stance and yowls alot followed by firm stomach. Eating just fine, drinking occasionally. He hasnt used the box too much tday but theres pee and poop in it.