Faster housing must be handed over to apply for real estate license. It takes at least 3 months to apply for a real estate license, which is usually normal for one or two years.

It is necessary and legal to pay these fees.

The so-called business tax is 5.5% of the difference

What is written in the contract is not for you to decide. There is a unified version, but you can add something, but you usually don't write such a request.

You don't need any help. Everything is normal and reasonable.