Nb4 wiring questions

[Greenkenzie]

Hey there,
I am currently working on only my second Saber install and was hoping that someone would be able to help me with a couple of questions. I am installing a Romans MK1 with a Rudy Pando crystal chamber. I am very much a beginner when it comes to the electronics side of things. I have looked through the manual and any info I could get and have arrived at the attached wiring diagram.
This is my first build with this type of switch setup. The switches will be wired into a 3pin SIP connector so they are removeable. One of these pins/wires from the switch is labelled 'AUX'. I am not understanding what this is for, do I need it and if so where would this connect to in my wiring diagram?
My second question is about the 5mm Accent LED for the crystal, this pad that I am connecting to on the NB4 is a 3.3v pad, does this mean that the board limits the voltage on this pad to this value going to the LED?
The accent LED has a forward voltage of 3.2-3.8v and runs at 20ma, so I am unsure if I need to resister this LED?
Any help would be much appreciated.