Is it some sort of inside joke for anime characters to hold guns wrong?

user...

you shouldn't be gripping the magazine directly. grip the magazine well.

Why is the selector switch where the ejection port should be?

>no charging handle
WTF?

On AK pattern rifles the safety doubles as the dust cover, the gun is on safe in that picture.

>gripping the one part not covered by a barrel shroud...
YIKES!

Apart from what's already been said, you're using your bone structure to support the rifle, which is also why you'd use an open palm or fist in this position and not hold the magwell, and why the OP picture is not an example of that shooting position - it's just a chicklean, really.
Do watch Rifle is Beautiful btw. My favorite from that season, as someone who shoots and is into olympic rifle shooting. there's a good chance you're going to enjoy it.

There is also usually a charging handle that is for some reason missing.

>colt industries

Don't put too much thought into it. The proportions are all kinds of fucked up.