US Diversity Visa Lottery is an example of a visa you have to take up within a limited period or you lose it. It's a reasonable question, DTV although technically a tourist visa is a long term visa that allows remote work.
this is correct, it's business only. And in many cases, smaller merchants like street vendors may be using personal rather than business accounts, so this could impact you more than that sounds. I know a lot of the smaller places around here that use QR, it's a personal name and not a business.
just going off what you posted: "I’ve lived in Thailand for the past 5 years on a Non-Immigrant B visa." People have switched from non-immigrant to DTV, depending on circumstance DTV may be a better fit for them.
if you're currently working on a non B you wouldn't qualify for a DTV, for what you're on your employer needs to be inside Thailand while for the DTV your employer needs to be very specifically not inside Thailand. Unless it's a job you can switch the employer to one outside Thailand, then DTV would be an option.
you don't need a return flight with a non immigrant visa. If you have a non immigrant long term visa you don't need the DTV. What's not an option is continually border bouncing on tourist entries. Non immigrant B is not a tourist entry.