2. Still no. The "ai" and RML use a different AVB than the SLIII.
3. Yep. The numbers (16, 24, and 32) refer to the number of preamps on the unit. They're all 32 inside.
4. I've had some luck using MOTU products with the SL III. I think they have a digital snake, but I haven't tried it, so I wouldn't be able to recommend it or any other snake. I just picked up the PreSonus 32R and using that as a stagebox. However, PreSonus just announced new network stageboxes that run over AVB.