Notice people, this IS the MBAC forum. There's no moon variations, so he definately can use the flame-pit.
Anyway, 22 A or B or C sets it, they'll drain enemy health. C is best since it does it best and also drains their magic bar. 22 A or B or C (depending on which you used to set it up) will ignite it and hurt them as well (usually a good idea to wait till right before it disappears on its own so you get the most use out of it).
As to the arc-drive, I try to only use it when I know they can't block; even then sometimes I save my magic bar. The command grab version is better, however I don't know if that goes through a block like a normal grab.