In my quest for better handling, whats next?

Nice work so far.
Don't forget that center dead-spot can also come from a worn steering coupler, idler arm play like a soft bushing, loosely adjusted wheel bearings, steeringbox movement, or even its mount on the K-member.
Even with a Borgeson steeringbox I felt a noticable improvement after I reinforced the mount to the K-member better.