Thank you to everyone that commented! With your advice I went back in and edited the design up a bit! The new module weight 7.10 Lbs.
The castor now has a second ring to keep the drive axle from going everywhere. Underneath the green ring is the thrust bearing to handle the axle load. I plan to make the green ring out of a new filament from Igus, the
iglide tribo-filament.
If you have any ideas for improvements or question please feel free to ask! I will answer any question to best of my ability! And thank you to everyone who has responded so far.