No, I am not wrong about this. Land borders crossings are limited to two per calendar year on visa exemption entries. There is no (theoretical) limit on any border crossings with a valid visa. Of course every border crossing (visa or not), is still at the discression of the immigration officer. Not sure what happened in your case.
Details of that subject are equally unknown, still. But if you want to avoid all taxes for sure, go with the LTR visa which comes with a Royal tax exemption.
Couple of still unanswered questions come to mind: 1) what about 90 day reporting - hopefully gonna be waived (or extended to 180 days). 2) will the DTV be available to all nationalities as long as they meet the requirements? We will see.
For sure. But at this stage that is likely to actually happen. From experience, there is a big difference between a concept published by either the PR or the tourism TAT department - or like now, by the MFA.