I hope these answers help you a little ... are you sure you have a BeoLink PC 2 and not its more recent brother the BeoPort?
Can I suggest you take a look at the BMLink and LinkPlayer threads in the Forum?
thatlondon: Problem 1
I don't have the luxury of using the Toslink approach, but my MacBook audio output port is dual - either electrical or optical.
Initially I split my cable into two electrical paths - one to my BV8 and the other one to my BeoPort (equivalent of your BeoLink PC 2) with its own BeoLab 4 speakers.
I found the sound acceptable.
Lately I have removed the BeoLab 4s and just use the BeoPort for its USB control and distribution over the MasterLink.
For local audio (as in your bedroom) I just use the BV8's speakers.
I now play my iTunes audio or my Front Row AV (downloads, or DVD) through the BeoVision by pressing "PC" on my Beo4 - if I don't want to see the screen but leave the music playing I press 'picture mute' ("P.MUTE" on the Beo4).
thatlondon: Problem 2
I am sorry, I don't think I understand this question.
thatlondon: Problem 3
Is there such a thing as a Masterlink splitter cable which would enable me to plug both TV and BeoLink into one cable?
Yes there is, your local dealer will have one for sale.
It is called "ML Distributor", and is a smallish black plastic box with 6 MasterLink ports on it.
thatlondon: With the BeoLink PC 2 I also acquired a BeoLink
Not sure what you mean by 'BeoLink' - the product section of this site lists 3 items under "Beolink" - one of which is the BeoLink PC 2.
Can you post a picture or a verbal description of this 'BeoLink' box?
First B&O (1976) was a Beogram 1500 ... latest (2011) change has been to couple the BL11 with the BL6Ks *sounds superb*