I'm pretty sure 'crystal' is simply high-purity meth•HCl (or sulfate). I've never heard of such a thing as meth•CO3, and am unsure as to whether or not such a thing could exist. In the case of a deprotonated carbonic acid (carbonate) you can have stable solids (such as baking soda (sodium bicarbonate)), but in the case of an amine salt the carbonic acid still has it's proton, which I would think would allow it to spontaneously dehydrate (breaking down to carbon dioxide and water) as you removed water from the solution. As far as I know it isn't practically possible to isolate carbonic acid in pure form, only as an aqueous solution in equilibrium with carbon dioxide.
At any rate, I'm very confident that MDMA freebase could be effectively smoked, although I'm not aware of any reports of somebody doing so. The process should be strait-forward (dissolve some MDMA powder or crushed pills in water, make the solution strongly alkaline with lye (sodium hydroxide), extract the solution with a non-polar solvent, then evaporate the extraction solvent to yield the MDMA freebase.)