The naptha layer is so thin because the jar is as wide as a barrel. Could the jar be dumped into a narrower container for an easier pull then back into the jar for another naptha bath. Not sure if the transfer would cause any harm.

First timer here

A good solution is to pull as much naptha out and put in a narrow container, the few drops of mix will fall to the bottom. Much easier to pull into the freezing container.

2 birds, one stone.

Yes you should be fine transferring the contents to another vessel. It's not ideal though and you must be very careful you don't spill the highly caustic solution on yourself. I use Mason Jars and a glass syringe to pull the solvent which then goes in a spouted glass pouring jug where I can then carefully pour the solvent off from any base material that came along for the ride. This way I only ever get solvent in my freeze container.

Yeah as said, the main problem is just stuff spilling out, caustic drops flying, possible big mess and danger to yourself. So be sure to wear safety goggles, gloves, long sleeves, do it in the sink, and have some vinegar ready in case a caustic burn needs to be neutralized.