The German line "Um das Gebräu wohl auszuhecken" does not translate to "breathe in the mixture from the vat". "Aushecken" means "to plot", as in "to hatch an evil plan".
It makes no sense for Nick to entertain the idea that he could return to a normal life just because he lost his Grimm powers. Besides retaining the knowledge about the Wesen, he has also made hundreds if not thousands of enemies in the Wesen community, both as a cop and with his extrajudicial Wesen killing. Without his powers, he is just that much more vulnerable to them.