[asid61]

The alignment of that worm gear is probably way off, with all those plates and screws.
If you replace the 6" drum with something like 1" and fix the worm gear you'll be fine. I still think a 2-stage versaplanetary will suit your needs, and it's going to be a lot simpler to implement than the worm box.
If you want to keep the 6" drum you will need to gear down a lot more. JVN design calculator will help you figure out exactly what you need in terms of motors and gearboxes.