Unit projectiles ignore furniture and fortifications, lord knows I've got more experience than most with this now.
I have no idea how often dorfs will try to grab walls to stop themselves in flight but I rely on it to keep myself alive as an adventurer by putting a weapon and shield in the same hand to keep the other free.
Now, what I was mainly posting about, there are certain skills which train attributes which you don't want to dump as an adventurer: focus, willpower, intuition, spatial sense, and kinesthetic sense.
Focus helps numerous combat related skills, willpower is important to keep from passing out from a broken finger, spatial and kinesthetic sense aid in aiming weapons/parrying/etc, intuition aids in blocking/parrying/dodging. There is a far too comprehensive list on the wiki about what skills raise said attributes but I know stuff like doing a bunch of knapping and wrestling small animals and such does tons for your survivability/effectiveness. I'm not sure what the most effective way to get dorfs to train spatial/kinesthetic would be but I'm sure there is one.
The armor skill and ground collision stuff is very true, I've slid like ten or fifteen tiles after flying across half of a 17x17 map and been uninjured or only had light bruising with tons and tons of "is deflected by the armorpiece" stuff.
I think the specific glances away message is when attacking material and defending material are equal or defending is better, I saw it when whacking at at a steel colossus with a steel hammer and bronze axe, similar happens when you take a copper axe to a bronze colossus. There is a size related component too though, as it happens sometimes with stuff like the freaky thick clothing on demon masters in gobby sites.
Oh, don't neglect mail shirts, they cover unique areas not protected by other stuff, helm+mail+gauntlets+high boots covers everything, then you add in the breastplate/greaves for full hard+soft coverage, with hood+cloak on top for facial feature defense oddly enough.