Hi gcruiser, Welcome...
If you bending teeth and tossing off the chain there must be a a alignment problem. The rear rag-joint, sprocket and tensioner work great if installed correctly.
There are different options,You may want to look into a Shift Kit from Sick Bike Parts LLC - Performance parts for your motorized bicycle
or a sprocket adapter from Manic Mechanic (CB-In Stock)
and Clamshell Adapters | Parts for Gas Powered Bicycle Motor Kits | Live Fast Motors - Gas Motorized Bicycles and Gas Powered Bicycle Motors