I feel you, brotherman. One of my dogs is getting pretty close now. She's probably the smartest dog I've ever had, and it's going to be rough without her.
In regards to consuming meat,
@CorradoSoprano4 nailed it above. Unironic "it's a tough one, man." Ideally, one would be in a position where you kill your own meat, or are close enough to the source that you can see that the animals live decently. This isn't feasible for most, I understand.
I do wonder why you jumped from "eating meat is cruel" to "I'm sad about my sick dog". Are you planning to eat the dog? I wouldn't say that's unethical exactly, just a bit odd. Somebody had to ask.