Mornin', Doc! Someone said I should pop in to my old haunt for a sec... My knowledge is pretty rusty at this point, but here goes:
The 3 LEDs are all for battery status - supposedly when fully charged you should have the green LED lit (I don't recall if the other ones were to stay lit as well). Phono jack is indeed for charging, but I think most of us Tribal users just yanked the 9v battery out and used a proper NiMH charger anyhow.
Stock board assemblies all looked like that, with the hot glue and soldered ribbon cable. The poor state of the electronics was my impetus for building the Warlord boards. I was wondering if perhaps you had a Fury chip installed, but the 'VEB' looking sticker means it's a stock chip.
Someone linked to the manual, and you should have all the DIP switch settings from that.
The stock LPR was rotten, but as long as it was lubed and functioning, it worked well enough. The biggest gripe was the lack of external adjustment. I still have a few of my old cocker LPR adapters kicking around - drop me a line and I can send you one if you like.
The foregrip reg, on the other hand... well, the old Sheridan RG-1 has better performance. It was downright feeble, period. If you can feed the gun stable (and adjustable) HPA pressure, I'd gut the reg and use it as a gas-through-grip to keep the stock look, just like you say.
I don't recall stock operating pressures, but I'd start at around 300-350.
Other tips/tricks... The ribbon cables are pinch-prone, so be very careful when re-assembling. Also, redo the hot glue strain reliefs with more hot glue or silicone - they were not very good to begin with (Romania is not well known for building quality paintball guns). I think I may have a few old Fury chips left (Defiance's version of the Chaos chip for the Tribal) if you want a simple drop-in upgrade. (Also have a bunch of Warlord boards left, but it would take me a long time to get around to final assembly of them.)
I liked to do a little valve work to open them up a bit - stick the valve body (tipped forward a little) in a vise and drop an end mill straight down to get a little more direct flow. Shaving the valve stem was a quick lathe job (your old Grizzly 9x20 lathe saw many of those).
As someone mentioned, the valve buffer is a very good idea. I also liked to give the ram shaft a good polishing, and long ago we found a cone spring from McMaster-Carr that was an almost perfect fit behind the hammer to help kill first shot dropoff.