1) Yes, you can use multiple. As I was recently admonished, presume the positive when interpreting rules text (that is, the cards "can" do things), don't get hung up on you/the card designer missing something - it seldom happens, and for any older cards they'd be in the FAQ for errata/restricted/banned so.
2) Val and Satin would be the typical combo to see out of a Night's Watch deck, particularly running out of House Baratheon with The Laughing Storm.
One of my favorite project decks is a Night's Watch deck. I struggle with TLS because thematically he is not as totally in synch as the other cards, but at the same time he is ridiculous powerful.
Because Val can be a bit difficult in reading to understand her power, her typical use is to activate her ability during Marshalling, before paying any costs but after having knelt some of your cost reducer locations (e.g. a street of steel and a fiefdom). If the first card up is anything playable in the Marshalling phase, you get to pay its cost and put it into play. Because it's a draw effect, you can do this 3 times and with little/no risk so long as you don't run with a lot of phase-specific events or a constricted gold pool. My NW deck runs in Winter and I struggle with that. I am liking the use of Night's Watch trait assignment to Baratheon Cards (via The Wall) in terms of really powering up my weenie 0-cost Heralds. I also find that the "Herald of the Stag" card can fit in nicely because of his ability to let you positively know you can play the top card of your deck the first time you use Val. Mine runs just two North agendas, for MIL and INT. All the Baratheons have POW anyhow, as do some of the NW.
FYI, though, this deck never wins (okay it has won once in its life), but does often aggravate people!