Regarding the rear wheel bearing failure concerns:
If it is the same arrangement as the Iron Barrel(which I suspect it is), then it is important to check that the bearing spacer that goes over the axle between the bearings is the right length, and is square.
This spacer sets the distance between the inner races, so that the bearing sits in the proper relationship to the distance between the outer races. If this dimension is incorrect, it will force the inner races too far apart, or too far together, and will ruin the bearing in short order.
This is very common in Iron Barrel bikes.
And the Iron Barrel bikes also use 6203, so I suspect it is all the same layout.
Don't assume that all the parts are made properly. Check things yourself.