Thanks. I hope it works out!
You seem like you know what you're doing, but since you mentioned it:
If you're worried about leaks, you can use Nylog White on the threads. It's food rated and works for your liquid and co2 gas connections. In theory, it's also not supposed to harden and make your fittings impossible to unscrew.
Looks like 3/8" NPT Schrader valve connection to me, but I'm not an expert on the matter.
The Polyformer is a 3D printer filament extruder created for people living in 3rd world countries with limited access to affordable filament. It allows you to recycle PET plastic from beverage containers by cutting them into a ribbon and feeding the ribbon through a heated extrusion nozzle.
When the tide rises, they should be drowned.
I'm allowed to say that here, right?