Based on those two videos, everything looks good.
A sensitivity of 1.4 for you looks good.
That's only 1/8th excursion you have going on there (looks like 10mm out of 80mm), that's well in the "safe-zone",
when the subwoofer starts to dimple or make nasty sounds that's when it's too much, closer to the videos I showed you
You seem to be hitting the 80 volt limiter, you could try bumping that up by 10volts at a time. Up to 120volts is about as high as you'd want to go.OR
You could try this settings file, it will give you a LOT more deep-bass, you'll be completely flat to 9hz with this one, and the subs will reach down to 5hz at a slightly reduced level.
This is the settings file that I currently run.
I applied some less-aggressive limiters to this one, than what you are running now.
(Actually, I run this one with the limiters completely off, because I'm crazy like that
You'll want to increase the sensitivity down from my 6volts and enabled your Y-spliter mode.
IT8K_LMS18.I-TechSeriesv2.I-TechSeries.zip 17k .zip file
Obviously this will allow massive amounts of infrasonic bass to reach the subwoofers, so start at a low volume until you get use to it.
Up until this point I've had you using a settings file that filters out a lot of the infrasonic content.
This file basically has the "training-wheels" removed;
you WILL get MAX bass with this (or near MAX bass at least),
but there won't be much to save you from the road-rash neither.