so not true. Use mdma first to push out serratonin then coke to block the intake from pulling serratonin from the synapse also probably preventing it from releasing as mdma causes the reuptake to release rather than uptake. That possibly means mdma after coke is blocked, but used before allows the coke to synergies and potentiate. Just a theory.
Edit : Reading your story I agree with meth.... Where MDMA has an empathetic feeling meth has a selfish feeling, but both are really the same. If you had another test you could separate the crystals under the microscope again and test the supposed meth from the rest of it to get a clearer picture as it doesn't take much for a reaction. Then test what's leftover from the separated stuff to get a better reaction. Really though you won't be able to split the whole powder.
As far as the smell it could be from something active or not. I would assume from byproducts producing the meth. Who knows though without sending it to a lab for analyzing with some idea of what it is to compare it against samples.