Hey! Congratulations on your success!
You can recrystalize your dmt to get rid of impurities like lye/mimosa remains. Another strong possibility is that your crystals werent perfectly dry, that they had solvent remains in it. Thats why you need to let them dry as thoroughly as possible, or you can redissolve them in some low-toxicity solvent like ethanol or acetone (pure, non-denatured ones!), and let it evap again, which will help getting rid of naphtha that might have gotten trapped inside the crystal formations.
As for the anxiety, yeah there is a certain apprehension that remains even with the most experienced users. Try to have your clear conscience and have done all your duties in daily life, and try to sit down and breathe deeply and set your intentions straight before vaporizing your dmt.
I suggest checking out vaporgenie, the vapour is so much smoother than smoking dmt, might also help with the nausea aspect.
Lastly, I definitely suggest closing your eyes during the experience and 'letting go'. It will pay off