I went back to the beginning and reread each of the posts. I would like to thank you for your advice.
So what finally killed the algae? To my mind, what impressed me as most useful were the 50% water changes (8), which certainly reduced the Flourish Comprehensive I had been unknowingly overdosing. Dosing can be hard - it's at the beginning when you know very little that you need the knowledge.
I have been working more on the Flourish dose, doing the math and the conversions. For my tank it looks like it's about 10 or 11 drops.