My Corsair DDR2 800 is 4-4-4-12 at 2.1v. The 6-6-6-18 timings are even higher than the standard for 1.8v DDR2 800 5-5-5-15.
Basically those are low quality memory modules or you have them clocked wrong.
Yes lower is faster. The numbers are the time in milliseconds to perform the operations listed . As to how much ........probably very little. You would maybe notice on a benchmark test but not in real world situations.