Being a Director is irrelevant. You need to work remotely for company with a contract that shows you can do so remotely. But as you're a director perhaps you could write such a contract?
Officially the 800k must be in the account for 2 calendar months before applying for the extension and must remain there for 3 months after, never dropping below 400k at any point in the year. But some offices want to see the money in the bank for 3 calendar months before applying for 2nd and subsequent extensions. Check your local office.
Nothing to do with a TIN, it's withholding tax on the interest the bank pays you, which you might be able to claim back if you do get a TIN and file a tax return