No need to remove the valve cover to check ignition timing. Regardless though, if the distributor is centered, that should be close enough to correct (at least not at max. retard) that we could rule that out as far as the temp. gauge.

So you got a new dizzy, and ever since the fan is wired to run all the time correct. I bet w/ the new dizzy (mainly b/c it's set closer to correct, more advance) if you turned the fan off it would eventually overheat at idle - not that you want it to though.

My temp. gauge on my '92 EX has never gone above 1/2, that includes when the thermoswitch stopped working and the fan would never come on. However, my timing was fully retarded back then, so I'm assuming the car never got hot enough to cause the temp. gauge to fluctuate.
What's important about these temp. gauges, to my knowledge, is that they don't continually move or update once they get close to 1/2 way(unlike older ones). It takes a more significant increase in water temp. before it will start moving above 1/2, and eventually to red. That's my understanding at least, may apply to all newer Hondas as well for all I know.