I suspect you need to square the entire front end starting with the rear end. I have to assume the shop guy knows what he's doing and NEGTIVE CASTER is the problem. Ever try to steer a shopping cart with one wheel pointed in the wrong direction? The caster built in to the wheel is supossed to allow the wheel to turn where it's needed. Ever get a cart that has a death wobble? Same thing is happening on your car.
Is it sad that a shopping cart makes you forget something at the store because you thinking about steering geometry's?