Depends on your local circumstances and the requirements of your closest Thai embassy. For example, in Germany, if you are self-employed, you would register your self-employed activity and could likely use that as proof. Or another thought: Just show your stock portfolio - afterall, they mention a "professional portfolio" as a means of proof. Best to check with the Thai consulate closest to you.
There is no explicit tax exemption with the DTV (unlike with the LTR). After 180 days there may be tax liability. Details of those still not fully clear.
You may. A) because that is how all multiple entry visa work in Thailand. And B) The Thai Ministry of Foreign Affairs stated it explicitly that is works like that.
I hear you and agree on most of it. And I feel for the locals whose needs need to be addressed and interests procreated. But I don’t feel for the hordes of retirees, a group that always had it much easier than folks under 50 to stay in Thailand.