Everything you’ve listed will increase lift, so you’re on the right path of thinking.
The goal of course is to get enough lift to unload the kart and keep it from binding, but not too much that you start overloading the outside tire and the kart starts sliding or hopping.
The stopwatch is the ultimate test to see if your changes are working.
If the kart isn’t lifting but your driver is managing to get it to slide, it might be his driving more than setup. I’m guessing he likes the front narrower because it causes the kart to slide less. If he slows his hands down a bit, he might like the front wider. It might take a slightly different driving style to adapt to a lot of these changes.
I would try your changes you’ve listed, and also try narrowing the rear track width. If you can’t get the kart to lift with all those changes, your chassis might be tired and may have lost it’s “spring” or your seat placement is incorrect.