From what you've written I guess you are like me from the uk and the wording in the parts you've highlighted in your post looks familiar from the embassy website. As I said in my previous post I would stick to what the embassy tells you to do in regards getting the relevant documents processed in order to prove you're single and then call (or have your wife call) the authorities in her Hukou area in order to find out exactly what they require. The expats you've spoken to are correct to assume that processes in different cities and provinces may vary but I find it highly unlikely that a medical test or letters from the Chinese partners parents will be necessary(they certainly weren't for me and my wife). I'd be careful believing what is written on the china.org website you've looked at. For one it's 6years out of date and secondly it doesn't reference where these requirements came from. The only way to be sure will to be call up the specific pencil pushers who will be responsible for processing the documents and even then I would recommend asking them several times as we all know that in china information and instructions tend to be leaked out a little at a time as opposed to just being presented in whole. however, I do maintain that marriage is by far one of the easiest bureaucratic processes you'll go through in china.

It would be good if you post your findings on this site as an update guide for others in your position.

Good luck and congratulations on the marriage