Nice break!
Your story of the thermostat in the vice reminded me of destroying mine in a similar way, while trying to get one of the long hard lines loose. I had tried lots of heat and PB-Blaster, with no luck. So I wrestled the whole mess out of the car, put the t-stat in the bench vise with the line sticking 6 feet out into the garage, and used the hard line (which I was going to replace anyway) as the lever arm to break the joint loose. What happened was that the line came off and took all of the aluminum threads with it. I had no confidence that the "thermostat thread saver" attachments would work on what was left, so I junked the thermostat.
I was picturing what would happen if the vice broke off the bench and came flying back at me. Nothing like applying a lot of force and then slowly beginning to realize that it's probably a bad idea.
Good luck
Scott