yes 500ml xylene is an insane amount for 50g, and evapping all for so little dmt is a near ecological disaster
robert, pulling mimosa with xylene will yield you a weird waxy/sticky/dark-coloured substance indeed, that is normal. I would say your biggest concern is solvent remains trapped inside that goo, so maybe better redissolve it in ethanol/IPA/acetone (non-denatured, pure stuff....) and evap again, to help getting rid of xylene traces.
Next time try to get some limonene instead, and/or salt out your spice with vinegar/FASA/FASW/FASI and then freebase that, and you will be able to reuse the solvent without the need to evaporate. In
this thread you can see how to freebase the fumarates to get pure freebase dmt.
Also, forget tin foil smoking, get a vaporgenie or smoke it sandwhiched between leaves in a bong.