FFS! You just need conformation from your Embassy that you're free to marry, ie never been married or a copy of your decree nisi if you've been divorced. It's not rocket science it's super easy!
To get the 1 year extention of stay you'll need 800kbt seasoned in a Thai bank account in your name for 2 months prior to your application plus the 1 years health insurance.
She'll need to get from domestic arrivals to international departures, check in, clear security and immigration then get to the departure gate. It all depends how busy it is, but I'd say you're cutting it fine!
The Non Imm O IS a 'retirement visa'. You can convert to this in Thailand with 800k in a Thai bank, the visa is for 90 days, as it runs down you can then apply for a 1 year extention of stay based on being 50 or over.