[#][F] Eric Minton - 7/27/2017
With the understanding that I'm not currently immersed in the relevant material, and my answers here are subject to reassessment —

Originally posted by Murcushio View Post
1) The 3e core says that in the Realm jade as a currency is forbidden to all but the Dragon-Blooded and their assignees. Is this literally true, or is it that jade is forbidden to all but Dynasts and their assignees?
Yes, it's correct. It's fine for a foreign Dragon-Blood visiting the Isle to use jade currency, and mortal Dynasts are regularly assigned the authority to use jade.

Originally posted by Murcushio View Post
2) The cash system. Does its exchange rate where it meets the jade system float? That is, does the Imperial Treasury always exchange one koku for an eighth of an obol of jade (a half-bit) and vice-versa regardless of the respective purchasing powers of the koku and the half-bit?
As I understand it, yes and no. The exchange rate was normally fixed, but was subject to circumstantial manipulation by the Empress, who would offer exchanges at favorable rates (via the Imperial Treasury and Imperial Purse) as an economic and political tool.

Originally posted by Murcushio View Post
3) Silver. Is silver still a "the dirham was invented, promulgated, and to a certain extent is controlled by the Guild as a way to compete with jade in a standardized fashion" thing? Or has that been backed off of
More or less. The Guild didn't invent silver coinage — there are good reasons to avoid jade coinage in the Scavenger Lands and distant Threshold, which are covered in Manacle and Coin — but they've put a lot of effort into standardizing the dinar and dirham as an alternative currency to the Realm's.