Hi, Josh
The use diameter for feedrate uses the, Setting's page, Set A rot. Dia. "value" to calculate the F speed in relationship to the part Diameter.
360 rollover, When the A axis hit's 360 it reverts to 0 deg. value, With out it checked axis will continue to count up and if you issue a A0 the axis will reverse direction.
Play with these settings and G-code to see how thay respond.
Chip