As usual, I agree with Gary’s points. I usually see the same contact patch you’ve shown here, where it extends to about half the outer wear indicator and I’m usually at max caster. You look like you’re actually picking a bit of rubber up on the outer shoulder.
It looks like you’re too soft on axle. As Gary said, it’s deflecting too much and wearing the inner shoulder. But it also looks like it’s a little blistered, possibly from the rear being over-stuck. Kart is a flat, wet noodle.
What’s your caster like? As Gary noted, the fronts will wear more evenly with more caster. If you’re picking rubber up on the outer shoulder and the rears look stuck, it might stand to reason that some caster will clean up the fronts and get the rear freer.