Not sure what makes you conclude living in Thailand while working remotely in Malaysia wouldn’t be feasible. I would know plenty of ways to make this work.
For your boyfriend it could be as easy as getting the new DTV visa. If he got a job in Malaysia and can work remotely from Thailand, that should be a prime use case for that. As for you (if you guys are not married), you would need to find another reason the get the DTV - maybe a recreational class of the Thai Soft Power category. There are many ways. Alternatively, you both could also be based in Malaysia and just travel to Thailand as tourists every now and then - either visa exempt or on tourist visa.
If you CHOOSE to extend within Thailand for another 180 days in lieu of just leaving and coming right back in, yes. But you can also border bounce every 180 days and directly re-enter for another 180 days without any additional cost.
People got approved already, yes. Impossible to say how many. Most consulates take a bit longer than just a few days. UK seems to be particularly fast.
Not sure if it would be available in Thailand as a foreigner (or if you would have to get it from authorities in your home country). Can't provide first hand experience. But here is a link for the respective Thai authority (maybe use Google Chrome translate):
Nice. Keep us posted. Questions remain: Will they accept non-residents / tourists applying for the DTV? What kind of proof will they accept for either category.