Don't measure grid voltage directly between grid and ground, your DVM will draw a little current FROM the grid and show false reading. That's why "half cathode voltage on the grid" you refer to is unreliable, it will vary depending on what meter you use to measure it.
Take a measurement across the 1.5k resistor i.e R15 on the 5E3x2 schematic. It should read ca 1.1V give or take. 47V on PI cathode or thereabout seems ok but do you have correct A,B & C supply voltages? What are they?