1. Perhaps, but not guaranteed. Depends what access the ICN check-in staff have. If they're contract, not TG staff, your chances are reduced. Can you do online check-in?
2. Yes, should be no trouble to check your luggage all the way through.
3. HKG is ultra-efficient. You should be able to visit the transfer desk at HKG (arrivals side, before you go through immigration) to get your onward boarding pass.
I don't know if I can do online check in as the ICN-HKG segent is issued by BD rather than TG directly. When is online checkin available? I may be able to do it at lounge at SFO?
I guess the next question is, has anyone done this and what are their experiences?