1) the Men of the Mountains presumably made the door and carved the symbols,
tho exaclty why remains a mystery.
2) I like Kimi's "spectrum of fear" idea, from Gimli through the Dunedain to
Aragorn, then the Sons of Elrond and finally Legolas. Makes sense to me.
3) Well Gimli presumably provided most of the details later on relating the
story to the hobbits. So it makes perfect sense that we would get most of
this part from his perspective.
4) The 1st time...I had no exact idea who this was. Aragorn's mutterings
about simbelmyne and mounds did link it to Rohan, but it wasn't until Baldor is
mentioned in the next chapter that i put two and two
together.