You leave which cancels your current Visa then start again either by purchasing a new Non-O before you return or getting one when you get back if you meet the financial requirements.
The Immigration rules have not changed for income affidavit, the counties that cannot use this method is because their Embassies have stopped issuing them which, obviously, your's hasn't
So? A DTV visa is just that, there are no different types like the Non-O. In the past people with Tourist Visas could not enter Visa Exempt as they held an active Visa but, on the other hand, people have been stamped in Visa Exempt when they should have been stamped in on a Visa such as a Non-O, so that works both ways.
When you re-enter on a marriage visa there is no need to present your marriage certificate so you seem to want to continue this scaremongering. Thailand has a tradition of honouring existing visas when the conditions for issuance change, it's called grandfathering.
and they might not as Visas from outside Thailand are issued by the Misistry of Foreign Affairs, not Immigration which comes under the Ministry of the Interior ;)