I had also read that DOW had the best grease, but had a hard time finding it. I am actually glad I couldnt get it as I believe the Haynes is the better option for this application.
My lab ended up with a case of the dow corning grease right as we were told to switch to apeazon for compliance reasons so it is all I've ever used. I'm a bit surprised it made that much of a difference for you as I usually have an extremely light coating on my joints. I wipe them and then rub them essentially dry with a lint free cloth. You sure you don't have a screwed up joint? You can always test with a cap to see what the pump can pull down to. Just add one piece at a time until you see the ultimate vacuum drop and you'll have your bad joint.
If you are pulling a better vacuum, you can always use a sous vide to control your temps at more modest ranges.
I will say though that your distillation rate is painfully slow looking. Any idea how long it takes to run a liter through?