re: Treaties
I think we could do just fine sorting out property and claims in space without bringing nations into it officially. Let them set up their own ways of governing themselves. If guys from China want to set up lunar mining next to guys from the United States, why involve either nation legally? Let the miners and prospectors organize their own rules and regulations, and set up whatever government they need for their minimal requirements.
Suggested reading: "Moon is a Harsh Mistress." Or, for almost all of us, suggested re-reading.