My corals are open comletely every day while the light is on.
One thing you may want to control is such a large temp. fluctuation. IMO, you should have a 2-3 degree change at the most from day to night. A daily change from 75 - 82 is not a good thing. It stresses things out! Just my opinion, but I have read this and heard it from others before.
Mine ranges from 80-82 daily and everthing is happy.