You can only apply for the real estate license after the delivery of the house. It takes at least three months to apply for the real estate license, which is normal in general for one or two years.

It is necessary and legal to pay these fees.

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

What is written in the contract is not your decision. There is a unified version, but you can add something, but you generally don't write it like this.

you don't need any help with that. Everything is normal and reasonable.