Quite simple and common error that people make when calculating probability or chance. I think you will find that your math is fine but your foundation is flawed. <G>

The numbers are not 2,3,7,11, or 12. They are 1-1, 1-2, 2-1, 1-6, 6-1, 2-5, 5-2, 3-4, 4-3, 5-6, 6-5, and 6-6 or 12 possible ways to have a decision on the come out roll, out of 36 (hey that's still 33%)

But start with 36 possible combinations and I think you'll get the answer of -1.41% for winning a pass line bet. Still one of the best in the casino!