Swamp monster help please!

Hello and thanks for taking the time to read.

We have a 20 x 40 foot 36,000 gallon concrete w/ plaster in-ground pool with a Pentair Triton II sand filter and Sta-Rite Max-E-Pro 2.6 HP filter pump.

My husband usually maintains the pool chemicals, but has been out of town for 4 days. It's been hot and we had the pool cover on. Then it rained for two days and we weren't in the pool. I noticed yesterday that overnight the pool was GREEN.

He had tested the chemicals (pH, alkalinity, chlorine) last week, and the pH was low so he added bicarb.

Now, when I'm testing the pH is off the charts high (greater than 8.4) using the HTH test kit. I added 48 oz of pH reducer last night, and the pH is still super high. I repeated another dose of 48 oz of HTH pH reducer this morning. The chlorine shows greater than 5 (ppm I'm presuming?) on the HTH test kit. I also added 8 gallons of liquid chlorine (this reading was a few hours after adding the chlorine.)

Compared to yesterday, the water is much more cloudy and blue/green in color, there isn't a smell of algae and much less green, so I hope that is progress. I don't know how much I can fix if I can't get the pH down?

I've swept the walls and as much of the bottom of the pool as I can reach, but I need a longer pole to get to the middle of the deep end. We have a vacuum, and I was planning on vacuuming whatever settles to backwash/waste once I can get a longer pole. The pool store doesn't open for another hour.

Do you have any other suggestions? Floc? More chlorine? I'm taking a water sample to the pool store to have it tested and get a longer telescoping pole once they open, but any other advice or suggestions would be very much appreciated.

Thank you,
Jessica