Without a schematic it might be tricky to offer correct advice.
Generally speaking though you are correct that you likely can run the bias a little cooler. The question is what would the reading look like? If you are reading a grid voltage, you would want it more negative.
To measure the cathode current, you would first have to know the value of the cathode resistor (if there is one) associated with the power tube or tubes. If you knew that you could then calculate the current if you were able to measure the voltage across that resistor.
Generally speaking though you are correct that you likely can run the bias a little cooler. The question is what would the reading look like? If you are reading a grid voltage, you would want it more negative.
To measure the cathode current, you would first have to know the value of the cathode resistor (if there is one) associated with the power tube or tubes. If you knew that you could then calculate the current if you were able to measure the voltage across that resistor.