Ken - Would a hood/shroud around the display help visibility on sunny days?
As far as Number 4, above, I use a VR electronic counter with a large display, mounted on my stem. I use this for all my 5k & 10k courses, but use it for reference on longer courses. If I am doing a marathon, I calibrate with both Jones and electronic, and have both "clicks" on my notesheet (I can also just leave them in the spreadsheet on my cell phone, and reference them from there. No chance of transposing numbers this way.). I then watch the big numbers, and since they only advance once per wheel revolution, it is much easier to stop at the correct spot with less wobble. When I get to the intended wheel-revolution count, I stop, and my Jones counter is within 15 clicks, or so, or less than one wheel revolution. Makes it much easier to do the longer measurements.
The VR is an expensive ($115, I think) electronic counter, but with proper wiring, it can decrement, if I do happen to be daydreaming and overshoot my split. But, you can get cheap Protoge cyclometers I am told, which can be set to increment once per revolution. Don't overshoot your splits, as they won't decrement, but this is a good alternative to the expensive electronic counter. To be used to get close to splits; not to be used as the measuring instrument.