The coolant temp in the reservoir is an easy question. That coolant doesn't circulate in the engine. It only captures / returns coolant from the engine when the engine temp reaches extremes.

I think I would have checked the temp of the coolant that is in the radiator, not just the outside. Warm up the car (with the radiator cap off) until you can see water circulating vigorously when the engine speed is raised. Then drop the thermometer into the coolant and read.

When you decide to flush the system, you may want to consider pulling the radiator and laying it on the ground so you can flush from the return side (bottom). It is possible that you will get more gunk out of the radiator with that method because it is reversed of the direction of normal coolant flow. It may also give you an idea of how well the radiator is actually flowing. I usually seal a garden hose to the bottom using an old piece of radiator hose. That way I can blast water through an get an idea of the flow by watching the discharge from the top. Obviously this is not as good as having the radiator rodded or boiled out, but it's the best I can do at home.