Well, the story ended yesterday. Though I am sad, I'm glad it's over. He's not suffering any more, and neither am I. Trying to figure out what to do and what was wrong was hell. I only hope I provided him a good life.
I did find a pebble in his "throat" and felt another one (possibly) in his 'gut.' I didn't perform an autopsy and don't plan to. He was approximately 10 years old, all with me, and don't have the heart to do it. I did notice a possibly bloody anus/booty and his dorsal fins were brittle. I took some pics and maybe I'll post. They have some views of the fish most probably never see, specifically of the inside of the mouth.
Thanks again for the support.