For the arcing, there should be some kind of grounding device... usually a spring or metal strap traveling across the funnel of the tube... that would keep the aquadag grounded. If the ground is not there, you might get juice jumping around in there.
If you can get a model number off the chassis, I can see if I have the sams for it. Sears usually had a number stamped somewhere on the chassis. They're numbers really never followed a pattern. Sometimes they were 3 digits, sometimes they were 8 digits. IIRC, they did use a metal tag that was usually rivetted to the chassis, but that might only have a serial number.