Yesit is possible to change the sprocket with the wheel on the ground, just requires a bit of moving the bike back and forth when you loosen off the chain.
In this is the danger that the bike will fall off the sidestand and on to you.
Best to get a friend to help if you are gonna do this.
Can't remember which way to turn the eccentric but you will see it happen when you turn the thing anyway as it doesn't take much of a turn to move the wheel a long way.
Torque spec for rear pinch bolts is 33n/m not sure what that is in pounds,shillings or pence.