The red roofed shops are Vendors and the brown fort-looking shops are Armories. So, in the North Sector, H10/E17 are Armories and H11/E18 are Vendors. They stock the same items but may not be open until the Redlines are cleared out from the sector.
Stat caps: http://serenesforest.net/fe8/class_cap.htm
All pre-promote stats are capped at 20 except for HP and Luck. HP always caps at 60 and Luck always caps at 30, regardless of class or promotion.
Ballistae are immobile, but fire at a range of 4-12 and have 15 durability.
The influence is a d100 check against a base value (95 for trusted, 80 for friendly, 50 for neutral, 30 for enemy, 10 for mortal enemy) modified for circumstances and the order itself. Rolling under or equal to the modified total results in a success (or success? depending on the order). Rolling over results in failure, though neutral+ units may still do it if it's a good idea, just because.
That is one long walk, but congratulations, you move at least four times faster than a medieval army at regular marching speed!