1978 W123 300D

I've replaced all of the small bits (temp. sending unit, thermostat, 212 sensor, temp sensor @ r/d) On the highway (70-75 mph) , my car has been running just between 175 and the next line (200?) on flat road, no hills, with the A/C on, outside temperature around 80 degrees. Yesterday, outside temp got to about 100, and with all of the hills in WV, I watched the gauge go above the middle mark by about 4mm, with the A/C on, climbing an 8% grade on the turnpike @ about 70 mph. It did come back down after I got up the hill ( about 4 miles of hill ). Also, when I park the car, temp. seems to go up about 20 degrees, but immediately comes back down after I start to move. Is all of this normal? I know my aux. fan works, as I heard it running the other day, but it did not come on until the gauge was halfway between the middle mark and the bottom of the 250 mark. Is this normal as well?

Thanks

Jeffrey