Christian,
1) You need to set the type of speakers first - and what sockets they are plugged into - then you need to set the speaker roles - here setting Right Front and Left Front to PL 2&3. You can change the default option for Video and audio separately to Speaker 2.
2) You should use the Pace Sky+ option in the STB choices - it should be there hopefully.
3) The PS3 is controlled by its own wireless controller, so won't be controlled by BEO4 (although you can make it if you want with extra hardware) - you do need to select the video and audio input though. To do this, you need to firstly select what AV3 is mapped to in the CONNECTIONS menu (V.Aux is a good one). You then need to add this to your BEO4. on the list button. Instructions are in the manual.
With regard to the other speakers, I'd certainly connect at least the Beolab 7.1 and put it under your screen and keep the speaker default for video as SPEAKER 3 - it'll make the TV much better - but then I'd connect up all the speakers regardless of room size!
I would say to get the awesome surround system experience, you should theing of the Beolab 2 when you move.