Discuss the ending

What an annoying ending, to actually make me spend time having to think about it.
Is anyone is still around who wants to discuss the facts in an open minded way?
If you just want to state your own cast-iron opinion, please make your own thread.
Sorry this is long, but I had to try and put some reasoning for my views. Rather than just making unfounded claims.

First, what points can we assume?

1) The Enemy
i)The enemy creatures are not normal humans. We know this because they live in underground mines and do not come out in sunlight.
ii) Their appearrance must be horrid, but not devastatingly so, we can tell this from the reactions of the victims who see them (on the video and at the very start).
iii)They have a below average understanding of technology, we know this because they horde stolen flashlights, but are not smart enough to use the car batteries for similar purposes.
iv) They are sentimental in nature (despite being killers) as they also horde childrens` toys. This also suggests that they have children.

Now, it seems to me that aliens capable of interstellar flight would;
be so hideous as to cause a greater reaction in the victims,
have a greater grasp of technology than simply pinching flashlights,
have no interest in human childrens` toys.
Likewise, ghosts would petrify the people who saw them, would not need lights or toys etc.
Those two ruled out, I am in favour of mutants.

2) Bodyswapping.
It certainly seems like there is some bodyswapping going on.
i) the dead girl is apparently working at the restaurant.
ii)The Dad`s admiration for the mororcyles matches that of the old man`s admiration for the car.
iii) Those kids act very strangely at the end.

If we can assume both mutants and body swapping, the question is, how do a bunch of dumb mutants manage to swap bodies?
My answer is- occult methods. In other words black magic.
i) They find what is probably meant to be a human skin, which has been decorated with occult markings. Could this be a primitive form of body swapping that was later improved? If not it still shows us a link between `the symbol` and the shedding of skin.
ii) They crazy guy is taken to the place where `the symbol` is made from cars, apparently for some kind of ritual. The cop knows to take him there, and the crazy man knows what will happen there. It is obviously a place where rituals of some kind are performed.

Questions I cant figure out:
How did they learn this magic?
What actually happened to the boy in the desert? Magic?
If the lady was such a big shot editor, somebody would come and look for her and start at the last place she was heard from (she made a phone call from the diner) and then see her unaccountably working there as a waitress. At which point surely the game would be up for our gang of freaks?
Why use cars to make the occult symbol?