Hi,
this must have been a hard hit to the device :-(
I also bought a RV722 "as is" several days before, but had a litte bit more luck with the mechanical parts....
(see
https://www.eevblog.com/forum/metrology/kvd-why-1-1-value-on-first-decade/)
If I were you, I would remove the "frame" with the 4 screws at the front (unfortunately you have to
desolder all wires from the calibration sockets, as you wrote...).
But then you have plenty space for your repair without touching the precious parts.
On the other hand you have to be more careful without this "safety frame".
Araldite (or 2k epoxy) only in the line of breakage would also my preferred glue, but why a waxed twine?
I would use a normal cotton twine to prevent contamination.
For the second decade: I cannot imagine that the ceramic is not broken into at least 2 parts,
a break only on one side is very uncommon. It is not visible at the pictures. And if you have two pieces,
you can bend it away to fill the lines of breakage.
I would not be afraid of popping apart in the future, because of the Araldite. Normally it will not break
at the same position, especially in that case of porose ceramic.
If it will be sit on your bench, it will outlive you, but if you plan to play football with it, I dont´know. :-)
As I said, it must have been a hard hit.
I have also questions: can you reach the 1.0 and 1.1 values at the first decade of your device?
Is there a c-clip at the shaft under the wheel like at the other decades (shown in my first picture)?
Or can you push the axis and reach the 1.0 and 1.1 values?