I'd disagree about tyre wear. My rears wear far more than my fronts (I use a harder compound on the front as well). Aim for 4mm between front and rear diameters (eg 50mm r / 46mm f down to 46mm r /42mm f)

As for slop, sounds like the balls/ballcups are worn - cheap fix is to take a thin plastic bag, cut a disc 10mm diameter and use as padding, you may need more than 1 depending on how much play you have.

I run 0 toe in/out, -1 degree castor on a L4.

Also check your width, the L4 is quite narrow and you need to shim it out at the rear - but wheels must be equidistant from centreline