That's assuming the myth was made by mortals. What if the ascension to heave by force is the law of the Aubris? We have our gravity and our speed of light and our quantum mechanics. We didn't make these, they are there before there were mortals. In the TES universe, the "laws" governing the whole place are what we are calling 'myths' - the thief, mage, warrior; taking heaven by force; ripping out somone's heart and taking their place; and so on.
But are the stars affected by the myths, or do those myths simply cause the birthsigns seen on Nirn depending on the stars?
As for why there's daedric armor in the Deadlands - possibly, the armor can only be made from ebony in the Mundus because that is the only substance able to 'contain' the soul of the lesser daedra. God's blood. Perhaps, in the realms of Oblivion, the base material infused with the soul is not ebony, but some other substance - raw creatia? :shrug:
It's certainly possible, I'm just using what I consider a more likely explanation, given the evidence.
The 'glass' armor and weapons shouldn't be confused with volcanic glass. The book http://www.imperial-library.info/obbooks/light_armor_repair.shtml indicates the material behaves more like a metal than a crystal.
Frankly, http://en.wikipedia.org/wiki/Volcanic_glass (if you want to bring in the Real World) is quite brittle, and you can't really shape it into arms and armor since it just fractures.
In Morrowind, I recall some interesting things; Glass weaponry was pretty brittle, and Ebony weapons didn't seem completely ebony; they appeared to be metal with ebony along the edges of the blade. Likewise, glass armor wasn't completely glass, and ebony armor was mostly chainmail with some plating lying over it. And of course, they made sharper blades than most metal equivalents. Oblivion seemed to forget all of this, but then again, I don't think any of us are really that surprised.
It seems that while TES may have sciences, they do not perfectly parallel those of reality. Just look at racial interbreeding, or Daedric physiology.