As Klaus mentioned, you may have already some excess current draw from a possible leak to ground, either from a defective choke or leaky filter capacitor. I suggest to open one of the connections between the rectifier to the filter capacitor and insert a DC-current meter. Without load, you should see no appreciable current at all. Assuming there is no stray current leaking to ground, and if your your previous measurements are correct, then I would suspect more than just the choke. Your mains transformer's filament section may also be a problem. Here is the reasoning:
1.8V across a 45Ω load (substitute for the EC 92 filament), means a current of 40mA is flowing through the choke. Since under load the voltage at the opposite of this choke has dropped from the unloaded 8.8V to 6.8V, the choke's resistance must be 125Ω [(6.8V-1.8V)/40mA], which seems rather high. Furthermore, if the open circuit voltage drops from 8.8V to 6.8V with the 40mA current draw, this would indicate the source resistance of the transformer filament secondary and rectifier/filter section to be 50Ω [(8.8V-6.8V)/40mA].
In order to have 6.3V at the filament with 150mA (= 42Ω load), the unloaded voltage should be 32.55V, if the DC-resistance of the choke is indeed 125Ω and the source resistance of the supply is an additional 50Ω [(42Ω+125Ω+50Ω)*150mA = 32.55V.
It is very likely that the DC resistance of the choke should be considerably lower than 125Ω, and the open source voltage should be considerably higher than 8.8 V.