Your evaporation rate is something you need to determine through experimentation. In my experience a good rolling boil will definitely lose you at least a gallon per hour, but if you are really concerned about it go with 5.5 gallons to start with.
Higher temps can lead to higher attenuation yes. But a .003 difference is so small that I would chalk it up to the error inherent in predicting final gravity.
Yeah those times are really too short.
1. Ideally a kolsch should be racked to a secondary after fermentation and cold conditioned for a few weeks.
2. Snapping it down isn't really an option, your lid will get blown off if the CO2 being produced by fermentation cannot easily escape.
3. Well...
If you are trying to stick to a defined style then your choice is generally pretty straightforward: use whatever has been used historically to brew that style. But if you start experimenting and moving beyond those styles then yes it is absolutely a decision your base on your experience, you...
If your fermentations are already going well without it then I don't think you are going to see much of an improvement with it. We bought an O2 stone setup simply to save us the hassle of what we were doing before: pouring the wort back and forth between containers. I don't think it has improved...
Yep I think this is the way to go, it's what Randy Mosher recommends in Radical Brewing.
And speaking of Radical Brewing here's an short excerpt concerning blueberries that may be of interest to you Merleti:
Good luck with your fruity endeavors :mug: