All questions can be answered by looking either at the official site or here:
Battle of the pass is said to be the following:
As Kentis, Adric and Jayko are out searching for the tower, they dont get any troop support of the reason that is battle of the pass- all soldiers are currently trying to fight off the rouge knights storming that place.
Indeed, Mathias ages fast. Im currently discussing with myself if I should reveal why in my story.
The old knights return under the knighting ceremony, but wont probably be involved in a storyline ever again.