1. classically trained.

2. Tatum is the only guy who Peterson was afraid to play for.

3. stroke left him for a few years without a left hand for playing.

4. Don't know much about jazz, really - but it's easy to hear how - I'm using the word "articulate" his playing is compared to some classical greats, like the velvety Horowitz.  "Crisp" isn't the right word - Lang Lang comes to mind with this term.  It's just that with Peterson, from what I'm hearing, each notes is so particularly enunciated - if that makes any sense.  (I'd claim the same of Alanis Morissette, who pronounces every syllable of every word with deliberate clarity....)

When I was a young teen he bought me (read: him) a snooker table.  Even when I managed some small proficiency at it, he could destroy me, one handed.  That was so frustrating.  It wasn't fun playing other kids, because they didn't know how to even hold a cue.   It wasn't fun playing him - and it was even worse when he'd deliberately miss a shot.  (no resentments here though.....)