I personally shoot for +/- 2, but I agree with magicka, +/- 4 is totally fine. COBB says +/- 8.
For breakpoints, I suggest 5.7, 12, 20, 30, 45, 150. I've had a lot of luck with them. They don't seem very linear, but that's the point. Your MAF table is exponential in nature. Having these...