So, when you put in on the machine and you have 4 degrees positive caster, maybe set it at 2 degrees positive and see how it does. In the old days, cars w/o P.S. usually ran negative caster. I would aim for 1/16 - 1/8 total toe in. Start at 1/4 degree positive camber and you should be fine. This should be a good starting point to play on the street, if you're are going to road course it only, you can tweak it from there.
I do not have a problem with any of that. Anything within reason. I do not see +4,+5 caster as unreasonable. IMO, the reason why 4 decades of oem A arm cars were spec'd @ -1 to +2.25 caster, was the inability to achieve +3 caster. Not possible w/oem A arms. Race cars designed for 'speedways' could have unreasonable caster for other uses. Earl should be able to change camber some w/weight jacks. My advise on tow in echo's you.
Anti-Ackerman geometry should have nothing to do with steering effort sitting still or traveling straight. I do not believe Earl will have a problem with that part of this. Steering effort @ 5 mph should be half that of sitting still. At 50 mph, his gf should be able to wheel it around.
It will never be a car I would want to parallel park.