[DG] [DG11] Which EV series autopilot system is the right one

[Santosha Too]

I have a 12 metre, 12 ton sailing boat that I cannot calibrate the autopilot. The St6000+ appears to work fine but I cannot calibrate the pilot. When I scroll through the settings on the control head I se a deviation of 46 degrees which is not even close to the 10 degree max advised in the manual. I have attempted to calibrate with a new flux gate compass but get the same results. I am convinced from reading some other posts that the course computer (300 12v) is bad and will need to be replaced.
Q1. Are then any tests that I can conduct to verify that the course computer is indeed the culprit?
Q2.which new course computer if any are compatible with my ST 6000+ control head or must I change out the entire autopilot system?
Q3. I have an Accusteer 17-12 hydraulic pump, which steering system is the right one for that pump, I am thinking the EV 200 for sail?
Q4. If I must change out the autopilot what other components must be replaced, I have the C120 classic plotter and a Simrad A150 AIS, plus raymarine gps, sounder, and speed log of the ST 60 family?

Any other info/suggestions you might offer would be appreciated.
Sincerely,
Paul