I had the plural problem with "Ironworks" the other day IRL. I usually settle for the null plural ("... with a Talisman in play, I gain two Ironworks") but after a few drink it somehow came out as "Ironsworks", possibly on analogy with passersby or some such.
Wow, more Dominion-playing linguists? Count me in.
As far as [hw] goes, I've heard it among some speakers in the southwest--perhaps due to influence from Spanish which has [hw] in words like juez, but it could also just be a phenomenon from older speakers of English.