You really need to do even the most basic research, because not a single thing in this post is correct.
Both a marriage and a retirement visa are a non-O visa. The O means "other" and covers many things, like volunteers, parents of Thai child, parents of foreign child attending school in Thailand.
You can get both a non-O based on marriage or retirement in Thailand, but the requirements for both are to show money in your Thai bank account for 2 full months at the time you apply from immigration.
A non-OA visa is a different type of retirement visa that is ONLY available from the Thai embassy in your passport country.
Having a Thai wife doesn't have any affect on disqualifying you from a visa. Why would it?
Normally METV is only available from your passport country, but there have been a few reports of people being successful in applying in Vietnam.
If the embassy finds out you entered Thailand, they might cancel your application. I've heard some of the embassies and consulates in Germany are a little flexible on that though. And the odds of them finding out aren't all that high.
Of greater concern is if the call you for an interview, but that's also not very likely.
You can apply for extensions, which are brand new extensions each year, nothing is renewed.
If you have a marriage VISA, the 90-day non-O visa, then you can only apply for extension based on marriage. The extension must match the reason for the visa.
The following year, you can apply for an extension based on a different reason, since you are not applying to extend a visa, you are applying to extend based off a previous extension.