Simple RAW for Pathfinder Thread V: Golarion Strikes Back

[Psyren]

However, I've never seen a GM who wouldn't let you reduce the armor check penalty of a shield via Armor Training, as it's kinda silly otherwise.

Armor Master's Handbook has a number of ways to reduce this penalty as well if it's proving troublesome.

A134: Mounts and other companions get their own turns, the only thing they share with the master is his/her initiative. Similarly, your mount getting staggered or knocked out would not restrict your own actions.