No downside to try to see it's approved or not. But many offices allow 90 days report "within 15 days and not less than 7 days before the due date of notification". Be ready for this. If your application is rejected, you have until 7 days later to report at the local immigration office.
, you can apply for Non-OA in the US with funds in your home country. If you want to apply for Non-O, you need to apply for 1-year extension in Thailand and it requires you to have funds in Thailand. Check requirements of them on the website of embassy/consulate that you aply for your visa through.
Yes, you can use your salary with a valid work permit as proof of funds, but, No, you cannot do it just using your work permit.
Go to your local immigration office to get their latest requirements for a 1-year extension based on marriage, especially for financial requirements for work permit holders.
Then you have to ask your employer to provide company papers including tax documents as well as your own tax documents.
If you or your employer cannot meet those requirements (or they don't agree to provide company-related documents), you have to use the banked money method.
, at most office allow you to apply for an in-country initial visa when you have 15 calendar days minimum remaining with your current stamp. Only a few offices requires 15 working days (21 calendar days usually) or more.
You don't have to do at the "original" office that issued your previous extension. But you have to apply for your extension at the office that serves your primary address of residence.
In theory, you go back to the entry point to correct the entry stamp.
No downside to going to the local immigration office to see if they can correct your stamp. The worst thing would be they say "No, you have to go to the airport you entered Thailand".
As you have a multiple entry visa, it could be easier just to go border bounce to activate a new entry on DTV than go back to the airport in Bangkok to correct the current stamp.