Carbon is not -18dBFS like normal HD? Also, how to use S/PDIF?

[CoreRec]

Looking at upgrading from an HD6 Accel system w/ HD I/O and Symphony I/O that's been extremely reliable.

Like others, I tried HDX, but found the latency way too high once plugins were added (44.1). Plus the fan was unusably noisy.

The latency numbers with Carbon are less than half what HDX shows - very impressive!

I have some questions that I can't find answers to (or are curious oversights):

1. How can I use S/PDIF with Carbon? I can't see a way and that would be a real bummer of an omission - possibly deal breaker
2. How can it be expanded beyond the 24 I/O (I usually use 28 ins, but 30 when the band has a keyboardist)
3. The specs make it appear that Carbon is -20dBFS rather than -18dBFS like normal Digi/Avid IOs - is that right?
4. Does it possibly have SRC available on the ADAT I/O like 192s?
5. How long before preamp recall will be enabled like PRE and MTRX?

Thanks!