First question,
Stateroom credits are NOT noted on your Docs. The computer system will have it and you will get a notice in your stateroom also so noting it.
As far as the second question, not knowing for sure, I would think not because the reservations are tied together and you are only allowed one DC credit per reservation, but I could be wrong.
Per DC Benefit book for 2003 " The onboard credit is per stateroom for each stateroom occupied by an adult Disney Club member"
There are black out days per the list which are: 2/13 - 2/21, 11/22-11/28 and 12/20-12/31.
The code to use is DC but you do need an active card.
KennyK