Nice system! Let’s see if we can help.
1. Powerlink Mk 3 will be fine, see the site sponsor’s website here http://www.soundsheavenly.com/faq/guide-various-types-powerlink-cable-bang-olufsen-use/. Steve can sell you correct cables. Ask him for any doubt!
Note that the BeoLab 6000 speakers have two PowerLink sockets. They allow you to daisychain them
2. That should be fine, the B&O products take ‘C7’ cables, these will fit also when the cable has the two round ends side by side
3. Sounds good enough
4. Correct, the amps of BeoLab speakers need their own power supply cables. PowerLink cables carry both L&R audio signal, as well as the signal to switch on/off the speakers. But not the power for the built in amps of the BeoLab 6000 speakers
Hope this helps a bit.
Let us know how you progress and enjoy the system!