I've heard that going to a shell in an unloaded chunk can cause suffocation, and that you're supposed to chunkoload the shell storage. I think the old version of the map gave you two free spot loaders, but the new version doesn't include the ChickenChunks mod so I assumed that the problem was fixed.
The new 1.1.3 beta gives you 2 free spotloaders, which are supposed to be used to spotload your sync shell.
The reason ChickenChunks is not in the game up til now is that sometimes, in very special circumstances, chunkloading can cause the chunk to become corrupted and get reset. This has already started happening to people playing the 1.1.3 beta. Personally, I have *NEVER* (knocks on wood) had a chunk reset and I've used ChickenChunk loaders on servers regularly since before 1.6.4.
I would personally recommend using Aroma Backup anyway. You never know what kind of foul bug will creep up on your and destroy your progress.
Does anyone also know how to lower the temperature outside, so what the exact heat source is and if it's enough to just replace the dust with stone or if I actually need a roof (plus even walls)?
I'm pretty sure the biome itself causes the base heat levels. A long time ago, it was generated from the dust blocks themselves, so people would build sky-bases and suffer from hypothermia at night due to lack of heat. I don't think this applies anymore though. If water comsumption is your concern, the easier solution is to work on getting a solid, automated water production system so you don't worry so much about your water consumption.
Here's how I deal with water production:
-Early game solutions are to put silky on an iron-or-higher hatchet. Combine this with the Vacuous enchant and leaf collection couldn't be easier.
-Then, an automated treefarm can produce so much water, it's no longer a limited resource. Combine this with some kind of auto filling mechanism and an armor stand for the camel packs, and this just becomes a joke to replace your empty camel pack.
-Late game, you can then utilize the Pneumaticraft Advanced Inventory Relay (I think that's the name of it) to remotely replace an empty camel pack on your back, completely automating the entire process.