question on blocked shot:

player A goes up for a shot, player B blocks the shot.
player A lets go of the ball before his feet touch the floor...

is the ball then considered "live" and either player can grab the ball and begin play / dribble ?

Official's judgment required:

If A couldn't release the ball on the block, it's a held ball.

If A could have released the ball on the block, but chose not to, then the release is the start of a dribble -- apply those rules.

If the block caused the ball to become loose, live ball, play on.

you have to determine if the touch by b prevented a from
releasing the ball. if the block or touching didn't prevent
the release A(A DROPS THE BALL) may not return to the floor with the ball or catch the ball before it hits the floor(traveling) or let the ball hit and then recover(illegal dribble)

10th boys. I'm lead, A1 goes up for shot underneath. Great block/stuff, as soon as B1's hand leaves the ball, it comes loose with what little strength A1 had left in his shot. Coaches couldn't even see the ball come loose, but I did, so I had nothing. A1 grabs the rebound before he lands (call it an airball), goes back up and puts it in while B1 is staring at me looking for a travel and B2 tries to cover defensively.
Right call?

Yes -- if you judge the block knocked the ball loose.

Although it's not an approved mechanic, you can give the "juggling" signal to let others know what you saw.

Thanks, Bob. After halftime, while Batman was talking to the kids, Robin calmly asked me what I saw with that no-call under the hoop. I explained what I saw, and he let it go.