yeah I think you could evaporate further and stick in the freezer for 24 hours or so.. you could also try alternating between fridge and freezer every couple of hours for a few days before the final long freeze, to try to grow the crystals bigger so they dont pass through the filter.
do you have msds for your solvent, by the way? im just curious how pure it is.
regarding the sodium carb wash, you have to do it when the dmt is all dissolved in the solvent, not when there is something precipitated. Check the FAQ regarding when should you wash or not.
good luck and let us know how it goes