Let's continue :
7 -> it's false. P2P networks aren't centralized and neither decentralized networks, they are acentral ones. If you remove half of the nodes selected in a random manner, they will still work. You can have a multitude of them under the same protocol, once again take a look at syncthing. If your syncthing nodes are down, they will change nothing on mines because yours and mines aren't interconnected. And no, my nodes don't need to rely on a central authority for talking together.
2 bis, on the last line -> So in first, as said in the previous post, DNS is one of the 3 core protocols making Internet working. If DNS are down, your app can't work, because Internet will be broken. About lying DNS, we have invented one or 2 things against it preventing the possibilities of impersonations and MITM.
But as you are concerned of being dependant of what makes internet, what about NTP (directly) or BGP (indirectly) issues in this case ?