Cats going deaf don't know their volume. When mine was near the end, I took her on middle of the night walks around the neighborhood, and I let her sleep on the bed. I certainly had the nights where she'd be yowling, and then look at me (noticing I am right here) and give a quiet "meh". I've seen ideas of having lights on, or night lights. Probably a good idea. Or at least a cat bed in that corner, with a favorite blanket, or an old shirt that you wear for a bit before putting it down as bedding.

The weight loss is a concern, though. Mine did that on the last year of her life, due to hyperthyroidism, then the slow death of kidney failure. I knew her time was coming when the urine sample was practically water. Eventually, the kidneys just can't detox the body, and fluids build up, suffocating them.

As for my cat's final days, I had the last nightly walk the night before putting her down. No regrets. She wanted it, and I let it. She was feeling well enough to try and be a cat one more time, and who would I be to refuse? Let her sleep on the bed, held her to the end.

The final decision is a hard one to make, but important to not delay if you know the time has come. Cherish the good times, and make sure kitty's last memories are good ones. They often do know when it's their time to go, too.