I put it back together with Loctite Retaining compound. Applied it to the mating surfaces of the gear and weight, as well as the shaft and key. Hopefully the extra retention strength will hold it enough that it won't shear another key.
I would have like the use Loctite 660 but didn't have any on hand; so I used the bearing retaining compound I had.
I will update if it fails but it won't get run hard enough to fail until I go back to the dunes.