have you checked to make sure they are at full brightness with the dimmer dial?
Regarding your panel illumination issue: Like Kidd I would recommend checking the dimmer dial first. Don't even need a key in the ignition for this test. Just select accessory/parking lights position on the dimmer switch and vary the dial. Brightness should vary while moving the dial.
If panel intensity does not vary you might want to try checking the output of the dimmer switch. Remove the switch from the dash. Using a VOM probe the connector pins on the back of the switch until you find one that varies in voltage while moving the dimmer dial. It should vary between B+ and a lower voltage. Don't worry, you'll know when you find it. (Not sure on the wiring colors/pins for your year so recommend looking in the wiring diagrams manual or online for your year/exact connector/wire/pin/locations). There is a panel dim reference (B+) and a panel dim output that varies with the dial position on the dimmer switch which you should be able to test by selecting the parking light position.
If you cannot find a voltage that varies on one of the pins on the back of the switch (and/or don't see B+ on the output of the dimmer switch at max intensity) you likely have a bad dimmer. Replace it.
If you do have a varying voltage on the output that can reach B+ but the panel lights are still dim then I would do a continuity test to ground from the dimmer switch ground wire to a ground on the body. You should have a tenth of an ohm or less.
Then I would chase the wiring and wiring connections through the SJB/BEC looking for good connectivity/ continuity, voltages, voltage drops and grounds. If everything checks out okay the problem may be the low current board in the SJB but I have a hard time believing that since I would think it should just fail completely (no lights) vice fail at a low voltage state.
In the majority of cases I would suspect active components first (like a mechanical switch/dial vs a low current board). Unfortunately, I'm often surprised by the types of electrical issues these cars have and how often the problems/solutions don't appear associated to the symptoms the car is experiencing more than I care to admit.
