Zero, have you tried RB?

Setting it up in RB and getting it working may show you what you need to change in BiaB.
I still think the correct input isn't selected in BiaB. When you click the VU's in BiaB, you get the basic windows sound applet?

RB is the sister program to BiaB, meant to do things more along the lines of the advanced audio you are trying to do.

Very likely you can run your VSTi's inside the RB program instead of standalone and have the control you want, plus you can easily record from multiple inputs (once set up correctly) and even send things out multiple ports for your 'surround' setup.
You can also still generate backups, although not quite the same as BiaB.

I do not work here, but the benefits are still awesome
Make your sound your own!