6.8.2 should have brought the firmware upto 3.04 so that is why you are getting the error. First make sure you are runnung the Updater associated with 6.8.2. All versions have there own updater and if you have installed multiple versions of Lake on your PC each has its own updater. When you open updater it should give you a target version of 3.04. If this is not the case I would go back to Lake and download the software agiain. Reinstall it and run its associated Updater.
The VPL switches on the back of the FP are for setting up the Voltage Peak Limiter. Ohms law tells us that Volt =Square Root (Power X Resistance). From Danleys specifications the speaker is rated for 2,8000 watts peak at 4 ohms.
Vp=SQRT(2,800 X 4)
Vp=106 Volts Peak
The closest setting to that is 121 or 101. I personaly would set it for 101 and then set the Limiter Mode for Soft.
If you are using more than 2 sub's on each channel, 2 in parrallel for a 2 ohm load, than the equation turns
Vp= SQRT (5,600 X 2)
Vp= 106 Vp
Clearly 5,600 watts at 2 ohms exceedes the output capability of the amplifier so you can leave it in the 155 Vp position but you will current limit long before you reach that maximum.