Now as to questioning my knowledge--well I question that all the time.

Doh!Herr Dr. Professor wrote:Here's progress, however slow--since November 23. If you are hurried, just jump to Q1 and Q2.
1) With yet more fiddling and head scratching, I discovered that a new separate servo works fine, whether connected to the FlySky iA6 or iA6B receiver. Contrary to my belief, the servo in the little 4X4 actually did not function.
2) I disassembled the 4X4 just enough to get out the defective servo. On discovering that the Servo was marked "Guo Hua" and "9g," I found online many quite inexpensive little 9g servos. I bought 6 of one brand and 4 of another. I also bought a servo tester, as Jofaur suggested. (The whole bill was less than $45US.) The tester is handy, handy, handy!
3) The servo tester confirmed that the installed servo was not working, even after I tried cleaning the contacts.
4) I found that the steering is a big tight, so I did a bit of cleaning and loosening, but did not overdo it.
5) In installed another 9g servo testing at each step. It worked the steering, except it was not centered. A quick web search of the terms "servo centering" showed me the way to use the tester to center the servo. So I took everything back apart, centered the servo as best as I could, and reassembled.
6) Now the working servo is installed, but it is not as exactly centered as I would like. I could disassemble again and try to re-center the servo, but it isn't clear that I could get any closer, given the gear-like mesh between the servo pinion and the servo arm.
So here are my questions for the next step:
Q1) After centering a servo using a tester, is there a way to even more precisely center a servo by adjusting the transmitter? That is, could I "fine tune" the steering servo through the transmitter in a way similar to the way one "fine tunes" the coordination of track speeds through a hobby grade transmitter or a transmitter such as that provided with a Taigen or HengLong tank?
Q2) Once the servo is centered to my satisfaction, should I use the transmitter to set the "ends" (FlySky's term) or stroke limits (i.e. the percentage of stroke) of the servo so it does not go so far as to cause the servo arm to contact the frame rails or the tires to contact the model?