The simplest thing for you is probably to get the Non-OA visa from your home country before you travel to Thailand. That gets you 12 months inside Thailand without having to worry about banks, leases, etc. It does require insurance, police check etc. If you like it you can either get a 2nd year out of it by doing a border bounce just before it expires with a new years of insurance or leave Thailand to get a Non-O and return
You need a full 12 calendar months of transfers of a minimum of 65k baht each and every month before you apply for your next extension. You must also honour the terms of your current extension, so 800k minimum for 3 months after you got the extension and never below 400k for the rest of the year. Sounds like you are going to have to bring your account back up to 800k two full calendar months before applying for your next extension (3 months in some places so check with your immigration office). Don't stop your monthly transfers and you can use them the following year
you can't do that as you are meant to apply via the consulate in the country you are currently in AND remain in that country until the visa is issued. Once here go to your local immigration office and get the handout for applying for an in country Non-O