1. Leave it, it can be used to adjust phase via distance setting.
2. I do not go that high but whatever you like is fine by you
. You won't hard the subwoofer, you just may reach its limits more often. I can think of a couple reasons why you like to boost the SVS hotter
- The SVS does not have a peaked response and therefore you can tolerate more boost before the midbass dominates
- You may be hearing deep bass for the first time and wanting more of a good thing
Anyway, you might want to try it on something a bit less starting out and then continue to raise if it still doesn't meet your preferences after a couple days.