When they put the car on the alignment rack, the biggest difference as a result of me moving the lower arms was the camber. The wheels were at about 2deg pos (the wheels were visibly tilted out at the top). The caster wasn't really all that much difference.

I think to get more caster, I need shorter sleeves. Both sleeves are as short as they can get (no threads showing). If I extended the length of the front arm, wouldn't that impact the camber setting too just a bit?

I think with thicker tires, you'd get a bit more road feedback. Maybe wait, then start cutting the spring if you feel that it's still too light.