There's caps on it. The top one is there. The bottom on is behind where the refrigerant goes in. The inner tube is completely surrounded by -40° refrigerant. Also this wouldn't be used for a wort chiller. It would have to be used with glycol to keep beer lines cold over a long distance. The wort...
I'll try to remember to take a pic tomorrow. It's not a looker by any means lol.
I evacuated the system, removed the evaporator, and brazed on the heat exchanger. I didn't measure the amount of refrigerant, I charged by superheat. It uses a cap tube. A txv would give you more control.
Put a dollar in the seal, shut the door, and pull it out. It should be somewhat hard to pull out. Do that around the whole door, and it will tell you where your seal isn't sealing.
That's the sloppy way to do it. The proper way it to remove the evaporator and install a tube in tube heat exchanger or plate heat exchanger. I have one sitting in my garage that I made that cools down to -40. Of course it could be regulated to be warmer than that.
Hop on TS sometime. You only need one bulkhead if you want to use that. Personally I would just run the hose through the collar and seal it.
Is the regulator on the tank your only regulator right now? Or do you have a manifold with a regulator on it too?