A very annoying situation for You,  gallows_pole, I empathize with You, having suffered from this predicament a few times.  You will most likely have to purchase workbench at a cost of around $100, or maybe seek some aid from a friendly and very sympathetic music store that could help you out in a pinch. However your weak volume string dilemma might be mechanical in origin. The problem string in question might not have positive contact with the piezo pickup embedded into the saddle piece. You might want to check and see if the saddles are racked out of line. Next, check to see that the saddle legs are even and not tilting the saddle, and finally try to keep the saddle piece parallel to the bridge plate. After all is said and done, as in a prerequisite, every variax owner should have Workbench. the variax internal flash memory is prone to corruption. The Best To You!!  Please keep us up to date and informed pertaining to Your situation and hopefully a fix.