Your 57 deluxe is self biasing in that the current and voltage draw of the tubes work with the cathode (positive side) of the power supply to “self-regulate” the power they receive. The only way to adjust this is to swap out the cathode resistor of the power supply for one of a different value and re-measure the voltages. It’s kind of like spinning plates- the plate voltage (ha), power supply voltage, negative current draw of the tubes, and resistance of the output transformer all act together to influence the bias current the tubes receive. If you are not comfortable working around the hundreds of volts of dc current that can remain in your power supply’s filter capacitors, even after turning the amp off, you may want to just leave it how it came from the factory and enjoy. Your tubes will be safe and your warranty will stay intact. adjustable-bias amps have a potentiometer in the power supply to raise or lower the current supply to the power tubes. I’ve never heard of a tech who was willing to swap out cathode resistors while you play, but I’m sure crazier things have happened! As for the smell, Id go with some of the others here who are much smarter than me- it’s fine until it’s not. Putting the amp in a dark room and looking for red plating is the best way ahead- if it’s not red plating, it sounds good, and the smell isn’t getting worse, you’re good.