On the issue of China hukou after changing nationality.

After renouncing China citizenship, you have to destroy your original China passport and China national identity card, but there is no express provision to cancel your account.

When applying for renunciation of China nationality, a copy of ID card and household registration book shall be submitted. If it is handled abroad, it is estimated that you don't need an account.

If you give up your China citizenship and go back to China to get married, you will be regarded as a foreigner. That's all you need for a foreign-related marriage: your current passport and single certificate are both necessary.