Metal armor as 11/50 and not 5/25. you are also comparing a mark 1 to a mark 2 armor. Comparing Metal mk II with ca Mk II is even less of a difference, 12/50 to 15/55
The ammo merchant sells ammo in packs of 100, it just lacks proper art right now and looks like normal ammo.
Lootable cars a being added with the next patch to increase the general item availability. Also, mines ar eplanned for later (in weeks though, not days)