1. The Dragon is a https://en.wikipedia.org/wiki/Ouroboros of cyclic time, thus a metaphysically rooted archetype. Alduin would be the dark side of that symbolism, but still Aedric of course. Still natural.

2. The souls empower the Dragonborn until he dies and those souls are reunited with the All(-Maker) to be emanated anew into permanent creation. At least that's the way it should be. Soul trapping and the concept of "soul" is a messed up rubbish in TES since they did Dawnguard. A soul is nothing like a ghost with a consciousness. It's the life's will. The mind on the other hand is in part like the "larder" which is lost upon death - the other more important part of it is stored in the All-Makers "storehouse" long before death (RAM and hard drive for people who think more "modern" than I do). Nothing can destroy that but it is limited while time is endless - thus the https://en.wikipedia.org/wiki/Eternal_return. If you play an instrument and you didn't do it for a long time, to discover that it doesn't take very much to retrieve the old skill and when you see how some people learn a new skill much faster than others (the "gift"), which are two sides of one coin, then you know perhaps what I'm talking about. (Modern neuroscience is the worst obscurantism of this wretched science religion of course...)