Silo on Apple TV

I finished it up and loved it.
The acting is great, Tim Robbins specifically I thought was really good.
Things that confuse me (I am not familiar with the source material)...
1) so the gas that hits them prior to walking up the stairs is what does them in? The reoccurring heat tape bit really payed off then!
2) so the original sheriff and his wife are dead?? They can somehow manipulate the video to show the bodies, but they are not actually there...is it possible they survived somehow?
3) that is A LOT of other silos! I would love to explore the lore and differences but that makes it pretty overwhelming. I imagine many--if not most, are extinct?
4) the 18 lighted key chain thing that Robbins has? I have to believe that these silos can possibly communicate with a limited number of other silos??