You need 12x monthly deposits of 65k or more to switch methods. You can’t go below 400k from your previous extension as that was a requirement for that extension.
Probably a good idea to put the account back up to 800k two months prior to applying to use the 65k method just in case there is any sort of glitch. If there was then you’d be back to square one without an option to renew.
To pay for their services in obtaining a bank account for you. They offer the service. You pay. Like any other business transaction. Hire someone to do a service and pay accordingly.
Why would a bank employee need to be corrupt? There is no law on whether a foreigner can open a bank account on any visa status, therefore by opening an account for them isn’t breaking any laws.
It’s just that the paperwork needed may be more than they want to handle so it’s easier to say no rather than actually do.