If one vacuum distills an impure freebase that may contain small amounts of mercury in the form of almagams and/or salts, could some mercury make its way into the distillate?
there (practically) isn't any mercury, because
a) it was reduced to the metal and thus was never in your organic phase
b) you conscientiously washed your organic phase.
U can try it yourself.
A good test is to precipitate Hg as HgS wich is L=1*10E-47.
If u cant see a precipitate u can be sure that no Hg is present.
:-)
As long as you perform the extractions and washes as per the write up and distill your FB, there won't be any mercury.