I think 81 is to high personally? I notice that when I'm at 80 my animals don't look half as good as when I'm around 78, but keep in mind all these animals are from different parts of the world with different temps they are used to.
Now, to address your problems. I think your feeding is fine. Your not overstocked by no means. That's a big tank for those issues. How long have the lights been in life? I find changing lights can help? I would buy a bunch of clean up crew, I'm a big believer in clean up crew. I can recommend a way to kill all the cyno, but PM for that. I don't want to freak people out on my cure to cyno. Keep on top of the suction, but you don't want to do that or have a second job. Are your test kits all new or at least updated? I'm amazed your PH is that high and your only dosing? I'm around 7.8 to 7.9 with the lights on in a good day and I dose. I would calibrate your APPM to double check that, but that doesn't have to do with your algae problem. I would up your water changes to once a week for sure. Stay on a schedule, just make yourself do it on one day every week. Oh, how long do you keep your fuge light on for? I used to have problems and cut that back to 12 hours per day and not 24.
I feed way more than that a day? I feed a sheet of purple sw when I get home from work and a huge pinch of flake before bed, but if you ask some people who have been to my house I stock mine chuck full of fish (what's a tank without fish right?) and corals. I do have a lot more water than you though? I also feed a huge frozen mixture 3 days a week. I would up the clean up crew, change the bulbs, unless there brand new, stay on the water changes, and check your test kits. I know all of the is totally redundant, but you will figure it out.
