He was 18. I found him on the floor of my study on his side, with his paws in 'running' position. He always comes down to be fed in the morning, at noon, at night. He always used to wake me up in the morning. This morning his sister - and litter-mate: they have never been separated, since birth...
Does your cat have kidney disease? It's very common. If your cat has kidney disease there are things you can do (my two senior cats have it), but first you have to know what you're dealing with. The concentrated urine suggests a UTI and/or kidney problem.
If she isn't blind you might try cat videos for her. Long shot, I know. I have two Siamese about your kitty's age (nearly 18), and they do yowl far more than they did when they were younger. However, I think their yowling may be different. Both have kidney disease which I'm managing with diet...
…also: good perception on the other responder's part. People who are cruel to animals have been abused themselves at some point or other. They are certainly unhappy. They certainly don't have lives (as in, "Get a life!")
Have you tried calling the police? I'd appeal to the "property" sense, saying this cat was your property and your neighbor destroyed it. I don't know if you can actually convict or bring charges. But this is unbelievable. In the meantime I agree with the other response: keep your cats indoors at...