My research shows that the "normal" range of CSF pressure is 10 to 20 cm. Anything below 5 is considered low and anything above 25 is high. The gray areas exist between 5 -10 and 20-25. Between those areas, manipulating the pressure, by adding or drawing off fluid and seeing if symptoms change is a better diagnostic tool.
It sounds like your surgeon is not on your side. Can you contact your neurologist or is there an advocate available at the hospital that you can contact? As the old saying goes, if it walks like a duck, quacks like a duck and looks like a duck, IT'S A DUCK!! Your numbers verify your symptoms. If you are not overdraining, maybe you have a leak. Either way, your CSF pressure is too low, in my humble opinion.