what do you find sketchy about using propylene glycol as a heat transfer fluid?
it’s certainly less toxic than ethylene glycol, and that pink color is probably beet juice in a formulation meant to be used in potable water systems for winterizing.
did you read the MSDS? https://contentinfo.autozone.com/znetcs/msds/en/US/220632
no, -20 C is not cold enough to do a proper dewax. I also suspect that the 2016 model also has a dewax column that is too small to actually dewax in (certainly the case for the 2015 model). you can certainly make decent product with -20C solvent if you get post processing right. although dropping fats out in CRC can get tricky (clogs).
the chiller originally sold with that rig could hit -40C with zero load, and -30C when actually chilling solvent.
@precisionnick’s calc for how much cold you need to chill a given amount of solvent are here: The ULTIMATE chiller calculator thread
did you use that handy search feature?
see (eg): Nitrogen assist assistance
you need a pressure difference to move solvent. so pressurizing your solvent tank with N2 is a great way to get it from there and into the material column. you could also push from there into the dewax, if there was room, and from the dewax into your collection pot. problem with that is that in order VENT your N2, you want to be (well) below your solvent’s boiling point, so you’ll need to know that…and understanding how it’s vapor pressure changes with temp would also be advised.
the engineering toolbox is a great resource, and the relevant link must have been posted 100 times around here at this point (Search results for 'engineeringtoolbox' - Future4200).
it’s probably even in Nitrogen assist assistance 
(turns out it’s not. try 70/30 solvent refill - #11 by cyclopath)
which makes it much easier to vent that N2…because it never leaves your solvent tank.