Am new to the forum and to Ceriatone amp builds.

I recently picked up a Ceriatone HRM BM 100 watt head built by Nik last year that I bought used on another forum.

It has some options I do not quite understand.  

I read the HRM BM manual, but these mods are not addressed.
I am not sure I understand how a couple things actually work or interact with each other on the HRM BM.

1)   The back of the amp has a Master Output level Dial on back (PPIMV)  by the speaker jack. Where should I set it for best s/n ratio? The amp is really loud with it up all the way, but really just want to know where it is best for overall amp tone. I may just leave it all the way up. I usually do not like attenuators except for my Torpedo unit.
2)   I can’t figure out the little toggle in front between the Mid and Bass. It is an HRM 3 way defeat switch.  What do the Up and Down positions do? The middle position adds gain and girth to the signal. I assume that is the extra tonestack? The up and own are supposed to be like a non HRM tonestack? The B/M/T knobs kind of work in the down position.  Not sure what the up and down positions do or when the regular B/M/T knobs are active. (see below).
3)   The standard Treble/Mid/Bass dials operation is confusing to me? They seem somehow related to the little toggle. LOL. The work fine in Clean mode with no green light (boost?) on the footswitch.
4)   The footswitch is also kind of a mystery. It seems like I can have the Clean on with no green light, the Clean on with a green light which is some sort of boost??And the OD on with or without the green light boost thing.

I have the Preamp Boost and Overdrive toggles in back set to Pedal.

I also have a Kleinulator which I am figuring out.

Anyway...any help or info is appreciated.
This is quite an amp.

Thanks.