you make it seem very difficult, yes if the person is a moron, you are probably correct. The process is not difficult, so for everyone else I would say the easiest way is to apply for the non-O in their home country first. They can then easily open a bank account here and deposit the 800k without needing an agent. They then have a couple of months to go to immigration for list of requirements and get their documents ready to apply for the 12 month extension of stay.
I have done a few online reports and up to now they have always been approved within 2 days. It seems like you have a problem if it's taken a week already.
Apply for a non O retirement visa online before you fly to Thailand. This will grant you 90 days and the option to extend your stay by 12 months (every year).
You will need to open a bank account when you arrive and deposit 800,000 baht immediately to qualify the extension.
you are welcome, you probably have enough time get the marriage sorted in time if you hurry (you can have the party afterwards). Good luck with whatever you decide 🙂