The +2, +3, etc. is more for defending the 3 point line than mid-mid/long range shots. The -2, -3, etc. not only helps by defending the post game but also helps you rebound.
Another thing I would consider is your line-up. I may think about moving Smith to PF and starting Davis at C. I realize he has his shortcoming's but he's your best rebounder by quite a bit, and you could use the help there. He also has a decent post game for a D-III player. Good luck!