Your Smartphone’s Battery Gauge is Lying to You (and it’s not such a bad thing)
The first 10% or so goes quickly for a reason. Don't worry about it.
As for the other issues, we really can't determine your issues without the battery stats graph screenshot. Not sure why you can't email them, don't you have gmail on your phone? Or upload them to google photos or something.
As for the screen banding, its possibly a result of the screen protector, or it could be the display of your phone. My first one had really bad vertical bands that were especially visible on low brightness. I ended up exchanging that phone the same day.
This is what my screen looked like. If that's what yours looks like, take it back.