[Mondial]

Yes, you are correct in that the tubes themselves add up to about 110 V, but there is also the additional voltage drop of resistor 18 which is 25 V. So in total you have the expected voltage drop of 135 V. 

If you apply less than 135 V then the voltages reduce proportionally across each tube according to its individual voltage rating. So if you apply 10% less voltage across the series string, each tube will have its filament voltage reduced by the same percentage of its voltage rating. So for the 50A5, it would have 10% less or 45 V, for the 35Z3 it would be 3.5 V less or 31.5 V, the 7B7 6.3 V  less .63 V or 5.67 V, etc.