Welcome! Come on in, we have plenty of room Crowded.
I'm not sure on your first question, as I don't camp at Illium.
The set breaks are pretty short, so if your intention is to see every set on the main stage, then I would plan on staying in the festival venue and eating there. You can bring food in, but no booze or glass. However, the vendors are awesome! I would definitely plan on eating some meals there, plus it's great to help keep the festival great by supporting them.
You will have a wrist band that gets you in/out so you can come and go as much as you like.
There is a second stage in town at Elks Park which most of the bands rotate through holding workshops and smaller more intimate sets. These can be really really good! This is also where the band and troubadour contests take place. Problem is you miss what is playing on the main stage, so you have to choose.
A typical day would be taking the shuttle in first thing in morning. Gates open an hour before the music each day. Plan for weather swings! You're at 8700' and during the day it can be quite hot, but will cool way down at night. So bring everything you need, you don't want to go back and forth from Illium. You can read about the line policy on the website, but I wouldn't to do that. You can set up where there is space as a base camp, and when one of your favorites is on, go up and look for an empty tarp. You can poach any empty tarp until the owner comes. Even then, if you start the process with a couple extra beers, you will make friends quickly and may get invited to stay as long as you like!
That's the Festivarian vibe that is so incredible!!
The last two sets of the day will be standing room only up front. Most people will have packed up their stuff before it gets dark.
I'm sure others will jump in with additional info.
I think you've just found you new favorite week of the summer!