it's the best option really. Trying to convert in Thailand requires a lot of trips to immigration and a lot of paperwork. Filing for an evisa is infinitely better
Should be fine. While there's no official limit to how many non-O visas you can get, the embassies would probably start to question it after a few. But a second one shouldn't be any issue at all.
Getting laid off would have no affect on a workcation DTV visa. Once the visa is issued, it's valid for 5 years. There are no further checks. You just would not be able to get an extension in Thailand, and instead would need to leave and return at least once every 180 days to get a new stamp.
There is no "education" DTV. There is an education visa, and a soft power DTV.
What the embassy want has nothing to do with getting an extension in Thailand. You can use almost anything to get the initial 90-day visa from the embassy.
Once you're in Thailand, you're no longer dealing with the embassy under the Ministry of Foreign Affairs, you are dealing with immigration which is a completely different government agency. So anything you find about the embassy and getting a visa is irrelevant at that point.
In Thailand, the ONLY thing you can use for the first yearly extension as an American will be 800,000 Thai baht in a Thai bank account in your name only. The monthly income method is not an option for you as the US embassy in Thailand does not provide income verification.
During this first 12 months while you have the money in your bank account, you can also be submitting monthly transfers to your bank account of at least 65,000 baht. The 2nd year when you go in for your extension, you can show 12 months of international transfers as proof of your income and stop using the money in the bank method. But you must ensure you keep your bank account at 800,000 for 3 months after you receive your first extension and never let it drop below 400,000 the rest of the time or they will not let you get any extension at all for year 2.
The embassy has nothing to do with those requirements so they have nothing to tell you about. The requirements to get your marriage recognized in Thailand are requirements of the amphur, banks and/or immigration. You'll need to go through the process to get all that done. As far as agents, there are some that offer that though I don't know enough to recommend some, but I've seen them discussed before. It can take a few weeks because a lot of it needs to be done in person in the UK then send back to Thailand with additional processes once it arrives back.