I got the custom rewards to work, which is awesome! But I found another issue.

It seems the pendants that up the chance value on the cubes you break have infinite durability. I have the max uses set to 10, but it doesnt break after 10 uses, it just goes into negative durability. http://prntscr.com/8la6x6

Edit: I'm using the most recent version available on CurseForge. If this was already fixed I apologize.

Should be fixed in the latest version.