It's not (or the equivalent amount internationally). The reason no one gets this visa is because you must have 3 million in a THAI bank account to apply, unless you're Australian and applying through the Sydney consulate.
Departure information and visa number are not mandatory information. Don't touch any part of the departure information and you don't have to fill it out. Touch any part of it and it all becomes mandatory.
No Thai embassy requires 800k baht. The DTV requirements are 500k baht in a bank account. A Thai bank account is not required and is infact impossible to open without a long-term visa.
Each year you can apply for a brand new extension of stay. You cannot renew anything.
If you applied for a 1-year non-OA visa from your Thai embassy which requires insurance as part of your application and then used that to enter Thailand, each extension afterwards will also require insurance.
seeing as how the going rate for a bank account is now over 10,000 baht, and that's for the few agents that still even offer it as a standalone services, yes lots of worries.
The only thing that could potentially be pending is their registration for the TM30 system. A TM30 filing itself is never pending, because it's just a database. When a TM30 is submitted, it's already in the system. Each TM30 just replaces the previous one. There is no approval, there is no pending, it's just done.
Once a TM30 is submitted, you must go back to the home screen and then search for the submission. Once the result is pulled up, there is an "Export" button that is used to generate the pdf proof. This is only possible for 7 days after the TM30 is submitted, as after that it will not show up in search results, and a new TM30 would need to be submitted if proof was not obtained from the previous one.
You do not get to decide. If you are married to the mother, you must apply for the extension based on marriage.
If you are not married to the mother and you have custody of the child and are the primary caregiver, you might qualify to apply for an extension as parent of a half-Thai child.