Under no circumstances should you evaporate a non-polar solvent in an open container, this will make you sick, it's not worth the health hazard. Unless you have a vacuum pump and chiller to condense the fumes before going into the vacuum pump, don't do it.
Your only reasonable option is to extract the non-polar solvent (heptane) with 1N HCl, separate, then add 1N NaOH solution to the aqueous HCl solution to precipitate the freebase DMT which can then be filtered out.