I'm not an authority on basses, just an old fart with years of experience who tries to be helpful. I'll try to make some recommendations based on what works for me. You may feel free to disregard them. The newer Tribute truss rods are dual action. I don't know when G&L switched to this. but I would think the dual action truss rods would affect neck relief immediately, and while there might be some slight changes the next day while it "settles in" with string pressure on it, you should see some help more quickly than that. Of course, not all "new" Tributes seem to have recent necks. In a post above, we saw an example of a player who bought a new Tribute with a neck whose serial number indicated it was from 2010. There's nothing wrong with that as long as it's not a used neck being represented as new, but you might have a neck with a single action truss rod. Nothing wrong with that, either. Instruments used them for years. Adjust either one in small increments--may 1/8th turn--and be patient.
A volume difference between neck and bridge pickups is normal as there is simply more energy in the string vibrations where they pass over the bridge pickup than over the neck pickup. This is more critical in basses like the L-series basses that do not have separate volume controls or a blend control. I try to get my levels as close as possible by adjusting pickup height. I've only been semi-successful that way, but that's acceptable to me. And I'm careful not to sacrifice the tone of the neck pickup by adjusting it too far down. Better to deal with some volume imbalance than to negatively affect the tone, IMO.
These are humbucking pickups. There should be no hum. I no longer own my Tribute L-series basses, but I never remember any hum in them. Try plugging it in to a different amp. Also, try doing it in a different room or in a different building entirely if possible. If the hum is still there, I recommend having a reliable luthier check it out or doing it yourself if you feel qualified. Also, consider shielding at least the control cavity with copper tape. Though most Tributes are shielded using shielding paint, the tape is better and easy to use.
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