Sorry for the delayed response on some of your questions that I meant to address earlier:
1. The Lich's sneak skill seems unnaturally high. That implies that there is some other mod that is changing the sneak skill values of NPCs, and that is going to alter how SDR works in relation to how it is designed.
2. The cap is the effective limit of the Sneak skill when applied to the detection formula. So 112 = 100 when applied in the script.
That still seems strange to me. I'd love to see a screenshot. Although I am having to redo the whole formula anyway due to the new movement rate multiplier features I'm swapping in.
Some examples how my ideal setup for sound detection looks like.:
-as novice it is almost impossible to get up to melee range to anyone
-an apprentice-journeyman can sneak walk past most things in clothes
-a journeyman can sneak run in light armor against the dumber creatures (skill < 25)
-an expert can sneak run past everyone in clothes
-A master can sneak run in light armor past everyone
-Running in Heavy Armor is always detected, unless you are master and the detector is a moron in sneaking
-Walking in heavy armor is detected either, if the detector has a high enough skill
-Sneaking in heavy armor with a skill less than 50 is detected by anyone.
I wouldn't say that moving soundless is possible, at least not at the speed you are sneaking in Oblivion. You might move quiet enough for a human to not notice, but some sound is always there. And it depends on the ground, too. In Oblivion this doesn't factor in, but I wouldn't go with the assumption that you are on the most forgiving one. Especially in most outdoor areas you have to move very slow and ?be good to not get heard, even without armor.
I would *LOVE* to factor in terrain, but according to the CS wiki, it's impossible for NPCs to "know" if they are grass vs. being on a road. Perhaps there is some otherway of figuring it out, but in all honesty, that would probably add too much processing load. Anyway, with the next version, you should have all the settings you need to properly tweak everything to taste.
Regarding the weapon noise, you are probably right that they don't make much, however I think the sneaking itself is going to be more difficult with a weapon drawn and the penalty should reflect that.