If you can fit 15" wheels and possibly larger tires, these will give you more tire choices including greater capacities.
But looking at your wear patterns, new wheels and tires are not going to fix things for you. The axle or its suspension are out of alignment, possibly because overloaded (even if you are not technically overweight).
It might not be an issue of straightening the axle, or replacing it because it is defective. Rather, it might be worthwhile to see if it can be replaced by something better, with enough carrying capacity.
This is one of the problems buying the manufacturers lightweight and/or entry models, we end up replacing the light components used to meet weight and cost targets with heavier pieces that can actually do the job they way we expected it. I've done a few upgrades on lighter trucks to get capabilities closer to the heavier truck I should have bought to start with; mostly wheels, suspension and tires.