Yes. Not available after 7 days although immigration may be able to see it. If they want you to provide a receipt you'll have to get your landlord to resubmit and provide you with a copy of the receipt
so many things getting mixed up here. Do you have a Thai SIM registered in your name associated with your bank account? If not that is likely your issue. Go and visit your mobile service provider and get the number in your name then go and speak to your bank
I think that most people with genuine accounts have nothing to worry about. If you had an agent open an account for you that's different, in which case I'd recommend you take your passport and go visit your bank branch and talk to them
Take the extension and get 30 days. Then if you need to border bounce use a border run company to do so. Highly unusual for 30 day extension to be refused