[Edi]

Encumbrance from armor reduces AP unless the unit is mounted, in which case it does not. Base encumbrance has no effect on AP. Limp IIRC cuts AP in half. Crippled cuts AP to 2, no matter the base value.

Attacking uses up all remaining AP for that round, but I'm not certain if it cuts into the AP allowance for movement of the next round (e.g. a unit with 12 base AP moves 6, then attacks, does it cost just the 6, or does it cost 12 and leave only 6 points of AP for movement the next round?).