Here's where I am now and I think this is a good solution for anyone with a similar problem.

I worked from the half way point and then out from there in either direction.

To get the carb barrel open half way with the stick at half I turned on the plane and radio with the wing removed, put the throttle stick at half on the radio, and removed the servo arm screw. I lifted the servo arm off the servo and put it back on while watching the carb such that the carb barrel was halfway open when I found the right tooth on the servo. Then I screwed the servo arm back down tight.

Next, I moved the stick on the radio to full throttle and adjusted the end point on the radio until the carb barrel was open 100%!

Last, I moved the stick on the radio to idle and adjusted the end point on the radio until the carb barrel was barely open.

Now, idle is idle on the carb, half stick is half open on the carb, and full stick is full open on the carb and full rpms on the engine! Before I was getting half open on the carb barrel with just a couple clicks above throttle on the stick. Didn't have to use any expo at all as most suggested. Incidentally, I ended up using the outermost hole on both the carb and servo ends.

This worked perfectly!! It's raining today so I'll have to fly the plane next and will report on how it works out.