I think I know where your camp was by looking at the trees in the background of the first picture. That part of the camp was a lot cleaner than ours, either that or these pics were taken the first day or two before your seats got stolen. You also seem to have good group of friends with you, we made friends with a group of younger Danes. You must have been organized and have arrived early to reserve that spot.
You always wanna be there well before the gates open. They're usually broken down in advance anyway, so unless you plan on camping in the line to get in you aren't gonna get the best spots. I think that's gonna be a bigger problem this year since the west camp is closed, full stop.
Also people stealing shit isn't that big of a deal really. I mean, pack your chair into your tent if you have a chair you care about, but in general you can just steal someone else's chair if yours gets took. It's all hippy and loving that way, although in a more passive aggressive way.
Oh and another thing. People never realize that there isn't snus in Denmark. We bought a fuck-ton on the ferry down and went around selling it to swedes and norwegians who willingly payed three times normal for a box.