What do I need to screenshot to prove I did the tutorial?
My submission was accepted. I took one screenshot of my profile page, and another of the home page, and used Irfan to save it to one image. To be honest, I suspect the profile page alone should be enough, since you can't get to it until you finish the 5 game tutorial
Quest 3 - Too Hard
I read some of the steam comments ahead of time and I found the same thing you're talking about. It's not a very active game. Most people who play, seem to play PvE, so stick to that to grind it out