The amp started cutting out, so I decided to swap the tubes. My bias meter reads a max out of 3ma of current, when it should be well into the double digits.
That's very odd, what do your plate, screen & negative grid voltages read?
R84 & R87 make up your bias "voltage divider" (Google this term), reduce R87 value by tacking a resistor in parallel, ONCE you are certain that there is nothing else adversely affecting the bias voltage.
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