"High" and "Low" volume settings? That's pretty bizarre...
First:
Is there any way to use the 950's room calibration settings while letting the LG do the decoding for true HD and DTS master?
The Model 950's digital bass management is not available, but the analog bass management is. I'd recommend setting all speakers to large in the player and setting the bass management switch on the Model 950 to "ON" so the bass management happens there.
Second:
Do you recommend turning the bass management switch on the back of the 950 ON or OFF? And is there a way to spike the volume some for the bass? (Yes I have the actual sub turned up, but could use more pre)
See above for bass management.
I don't recall anymore if the Model 950's trim settings were applied to the 6CH input. You could always test it by bumping one channel by 5dB and listening to hear if it makes a difference.
Third:
Is there a way to spike the surrounds just a tad using the 950? (The LG has the limit of high and low volume and all the channels need to be at high...believe me)
If the test above works, you can use that - but it will affect all other sources, as well.