do you have your upper floor windows open/cracked during the day to release the heated air?
I would do a combination of things, if feasible. Large shady overhangs and then allowing the upper floor heated air to escape. As the hotter air rises, it will want to continue to rise, so a few of your top-most windows cracked can help move air through. Lots of houses down in the south have this passive air cooling tower/cupola at the highest point of the home and then allows the hottest air to vent out instead of being trapped in the house.
I would also strive to prevent hot air from building up in the house in the first place, but you are doing a lot on that front already by closing curtains and such. We get pretty sweltering, humid summers, but a combination of opening all the windows at night, then shutting them first thing in the morning before it heats up and closing the curtains keeps the cooler air in, and then we leave for work to prevent warming the house with our body heat. As we are gone most of the day, we usually come back to a relatively cool house that didn't increase much in temperature. We live on the top floor of a small building, so we are perpetually in the hottest part of the home :)
But if we are around to warm up the space with body heat, then we usually close the blinds but crack all of the windows, and run both a ceiling fan and a box window fan to circulate the air around and out as much as possible.