Whodathunk that distilled water would be hard to come by. I tried to get some for big industrial batteries, not easy in the age of hoarders.

The action wrench is easy enough to make in a whole bunch of workable styles if you have access to any machine tools.

I take it that your barrel is now clocked so when tight your sight is lined up correctly. It is possible to drive the reamer while screwed to the action. If it just needs a couple thousands to get the headspace correct that is a piece of cake driving the reamer by hand. If the chamber needs a bunch of depth on the reamer, it probably will be easier to pull it off and finish it in the lathe.