End Gateways acting up; end cities not spawning

So first of all, when I spawned in the End, a lag spike hit and I fell off the edge, so I went into Creative Mode to save myself (I was having a bad day; I wasn't about to lose my stuff), but when I went back into Survival, I noticed that my armor display on the HUD was gone, and the Endermen, fall damage, nor the Ender Dragon could not hurt me; I was basically invincible. This is obviously not meant to happen.

After I killed the Ender Dragon and it spawned the End Gateway, when I used an Ender Pearl through it, it kept on teleporting me to my spawn on the Main End Island. I slayed the dragon one more time and I teleported through the new End Gateway, only to find myself back at my original spawn area in the End. Another glitch...

I flew in Creative Mode for tens of thousands of blocks, and although I found plenty of Outer End Islands, there were no End Cities to be found. After three hours of searching, I gave up.

Later on, I returned to the game and did the command /locate EndCity, and it took me to a mere 400 blocks away in the middle of nowhere, pretty close to the Main End Island itself.