Due to research (which many people don't do) I was familiar with most of this. But it is always good to read it. I am sure there will be plenty more silly and repeated questions, with people not checking previous posts and pinned topics, but thanks for always keeping everyone updated, and using your own time to do so.
Ask your airline before flying. If you get a 90 day Non O based on marriage, you are unlikely to have problems in Thailand, but they can ask for an onward ticket if they want to.
Send a message to the owner before you book it and tell them you will need their documents to submit a TM30 (if you do??). They will soon tell you whether they will provide them or not ;)
You know what he means ;) especially as he wants to get it in country. Non O and extend. "Retirement visa" is a term that has been used for decades ;). OK it is not correct, but widely used.