My dog is dying of renal failure. He is drinking, but has now not eaten in 14 days.?

I am now comfortable putting him down. Though he is not himself ( sleeping, laying down most of the day) (he will still go out for slow short walks), he doesnt seem to be in pain, but obviously is not doing well. I keep hoping he with peacefully p in his sleep. I dont want to be cruel letting him 'starve' to death. How long can a dog hang on w/o eating, and w/ kidney failure(high levels)( from lyme poss) . What will he have to go through ( the dying process)in the coming days if I don't put him down today or tomorrow.