They don't want you to become too independent. They don't want you to process your own nuclear fuel and so on.
I agree with you on this point, that Russia has a vested interest in maintaining the balance of power in the middle east so no one side gains total control.
It's a foregone conclusion that China will enter the war if America dares to start something with Iran.
China depends on delivering a higher standard of living to its people to maintain stability. The money to do that comes from exporting to the US more than any other single country. China is not going to go to war with the US, because it would loose all that export income and it has nothing to gain from such an action.
You're right that they also have an interest in maintaining the balance of power so that America doesn't gain control over their energy supplies, so they will react with political and economic pressure at most. Or, they will just wait it out and provide covert support to Iran.
Regardless, Iran will be able to depend on neither Russia nor China for help.
Hezbollah is the only ally Iran will have.