First of all, Congrats and Well Done! The intake manifold and swirl flaps look nice and clean. Obviously, the operating temp is improved. I expect you'll find a nice improvement in mpg as well.
I believe your are fine with the coolant. First of all, check out post # 17 in
this link. It is a graph showing coolant temp over time, and it took 8-9 minutes before temps got up to the 80's. So that is right in line with your experience. Also,
according to this link, the engine temperature sensor is in the engine block itself, not in one of the coolant hoses. I may not understand things correctly, but I have a hard time imagining how a potential air bubble around the thermostat/water pump would give false temperature readings from a sensor in the engine block. I suppose an air bubble in the engine block itself might give some erroneous readings, but I would think those would get flushed out quickly. From another perspective, if you had a radiator hose leak and all your fluid drained out (the "ultimate air bubble syndrome"), you'd still expect the engine temperature sensor to alert you to a high engine temperature. For what it's worth, I remember having to add another 100-200 ml of coolant after my first drive as well.
Good job and enjoy the ride!