All structures would benefit from having damp proof foundation as damp would cause tearing in the foundation structure and weaken it over long time exposure.
First you should spackle all the holes in the wall, if not done already. Lightly sand with a 150 fine sand paper. Wipe down with a rag to get all the spackle and dirt off the wall ( the paint will...
Typically you see the bar spaced at 12" o/c. But depending on the height of the walls reqd, the soil bearing capacity, foundation loading, geographic location and other site specific details, there...