Steps per rev should be 200 - most of the steppers we use are 1.8° variety.
Driver microstepping - I don't know what driver you're using and I'm not familiar with the Sherline mills. Either 1, 2, or 10 most likely.
If the steppers are directly connected to the leadscrew then 1:1 is the ratio to enter. If not then count the teeth on the pulleys and enter those #'s in the appropriate locations.
Leadscrew pitch - try turning the screw and see how far it moves the table in 1 turn. That is your pitch.
Velocity and acceleration are variables you need to decide and test - on what I know about the Sherline's size, start with a 50ipm max velocity and use the "TEST THIS AXIS" button to check and see if it moves without losing steps. Acceleration - start low and ramp up to see what your setup can do.
A axis - similar setup but you need to check using the same methods.
If you're using metric units, adjust commentary above to suit.
Maybe a Sherline user will wander across and give you some better #'s to start with. In the end, each machine gets tuned to work at it's own peak potential for what the user wants/needs it to do.