At risk of repeating myself at some point, lets explain why those "issues" are already addressed... with examples in the real world. In florida if you are caught using comercial space for your "main residence", you are hit with a 10 years claw back, 50% of penalties and 15% of interests on those 10 years that you left unpaid. Also on the same state, you are counted by actual household not just "household on paper" and courts rejected that "loophole". You could further disuade people from trying to pull that crap by putting into law that if they don't pay on time the acure interest too while the case is solved.
About 3, the exemption isn't total. It's a flat land-value floor, the same for every household, set from median income rather than land value, so it moves with what a typical earner can afford rather than with the market. Below that floor, land goes untaxed. Above it, you pay like anyone else. If your land's worth outpaces that floor, that's the market saying it's better used commercially than as housing you can no longer actually afford