My source (Food & Money in Ancient China - Swann) states that the catty of gold was 244 grams (~14 AD). It then goes on to state that the ping of gold was a flattened Chinese cubic inch of gold at about 940 fine (the balance being silver) that had a mass of one catty. Does that agree with what you know?
My observation is that the 244 g. "pound" is very light, and would only be useful when measuring precious metals IMO.
Other values for the catty are much higher as the mass of the tael/liang jumped up from 15 1/4 g. to 37.31 g. (Ku'ping tael). That makes the catty 1 1/3 lb.av. and a much heftier sum.
Gold in China have never become kind of currency, instead they have been treasured by people now and before, anyway. It is unusual for people to use gold as a trade media, normally gold have to be exchanged into legal tenders (cash coins, silver) for circulation.
You raised a very good instance about the gold in Hsin Dynasty, Emperer Wang Mang did renounce to cast gold coins, however, most of the historians world rather to consider that it was just putting on air, no one have ever seen those gold coins before. Gold has been respectively rare in China, however, according to our letter history, West Han Dynasty - the preceding regime of Hsin is an exception, in its royal treasuries were always full of gold, and its emporers were used to rewarded someones with special contribution with gold, but such scene can never be found in any of its succeeding dynasties, those tremendous of gold were suddenly dissapeared.
According to some recent researchs, historians believe that owing to the exchange rate between gold and silver was much lower than the same in the western world, Persians learnt to make profit on shipping silver from the west (Mostly, Roman Empire) to exchange gold from China, after a few decades, China had already lost most of its gold.