Wow, interesting. Well good on ya for doing it all!
One of my favorite guitarists back in the day had very stubby, powerful looking fingers. He was a young guy and not a manual laborer, he was just built that way, but oh how those fingers, which had a hard time all fitting on the fretboard, could just push those strings all over that neck and assault hard rock and blues thru his black les paul. Monster vibrato, too. Good stuff.
"I really do think my hands are much slower than they should be from many years of manual labor building up the muscles." Lifetime musicians, their fingers are obviously strong and capable and developed, but do they not get thick like a laborers fingers even though they get all that exercise?? I presume the answer is "no" but I'm curious for your thoughts, Dave.