Seems your BL passives don`t understand "PC". Maybe all your passives need a sw update, but I`m not quite sure if this will work. Ask your dealer. I got a BL active that does not detect "PC", but the BL3500 in my bathroom does.
As I understand it, Your BV7 should be V.OPT 2 (videomaster for video- and audio sources). The passives should be L.OPT 6 (slave for video- and audio sources)- I assume that N.MUSIC and N.RADIO work in your linkrooms....(?)
No, you don`t need a Beoport. Beoplayer on your PC connected to the same network should do it. You can access BM1 directly from your PC, or via Beo4 with N.MUSIC and N.RADIO commands.
But if you want to listen to your PC via your linkroom speakers you have to connect the PC audio out to your speakers. I have my Mac mini (with Beoplayer) connected to the PC input of my BL-active. But afaik BL passive doesn`t have an audio input. So use your Beoport for ML, PC input and IR and connect your BL passive via Powerlink. Maybe this will work - I never tried that....maybe there will be a "PIN4-problem". Soldering PIN4 to PIN1 should solve that.
Stefan