Three Sets of Cylinders for Front Loader?
Your comment about three sets of cylinders doesn't make sense. I only see two sets. The bent arm on the front loader makes a big difference though.
New gearbox assembly
How about implement the Reducing loads on the shafts and bearings idea? I mean instead of double the width of all plates weld the 4x4 tube (with shaft inside and bearings on the ends) next to existing plates. Also this chain gear makes big load to motor shaft, i think this shaft must also end with bearing mounted to the plate. Please consult with someone with constructions stress analysis skills. Btw. great work with LifeTrac design, i like it.