My L1 is finally in my room and it feels like Christmas in August

It is truly an incredible piece of gear even without X1.
As a new CH owner I have a couple of questions:
1. I have too much gain with my Lampizator dac when I use 242 output tubes, and it creates audible distortion. I was hoping that Input Gain setting would help to solve this issue, but it looks like I still hear some small distortion even at the lowest possible setting which is -6 dB. But according to the manual the gain is adjustable from -24 dB to +24 dB, but it does not go below -6 dB. Is it a mistake in the manual?
2. I assume that both XLR outputs are the same and it does not matter which one to use?
3. Shall I place the supplied plastic support discs under each foot even if I do not plan to use the adjustment spikes?
Thank you in advance.