Aurora 8 - Using digital and Analog

I have an Aurora 8 which I am linking to a Steinberg MR 816 CSX via setting up an aggregate device on my imac.
I am using the LT-USB card for usb link to Mac and a thunderbolt to firewire connection for the MR816

I am physically cabling hardware devices to both the digital AES connections on the Aurora and the Analog connections.
Tc electronics M3000 and Fireworks via AES and ADesigns Pacifica to the Analog Ins.
I am using Cubase 8 Pro as the DAW on the IMac. I intend to use the M3000 and Fireworks as external FX in cubase routing to them through the Daw.



I understood I could use both the digital and analog connections together on the Aurora 8 giving me 16 channels.

However when looking at the aggregate device I see only 8 channels on the Aurora so Cubase won't see both digital and analog at same time.

Qu 1 : How do I set the Aurora 8 USB to 16 channel mode?

I intend to use the Aurora as Master clock and link the Aurora and MR816 via wordclock cable.
The MR816 supports sample rates up to 96khz

I note section 5.1 in the LT-USB manual states that the sync source can only be set manually if usb cable disconnected.
However if I do this , then reconnect the usb cable it reverts to 44.1
With the cable connected I also not the ARC software greys out the sample rate settings so I can't change them from there either.

Qu 2: how do I set the sample rate on the Aurora to 48 or 96 kHz and do I lose channels at higher rates?

I note that the OS X Yosemite Audio Midi setup does let me change sample rates which are reflected on the Lynx but these are not retained when switching out of that app.

Any help appreciated

Thanks
David