Water continues to clear. It is no longer cloudy, but not yet crystal. PSI suggests backwash tomorrow evening, will shoot video if not raining and lighting decent. Hopefully it will give anyone who gets impatient towards the end of a long SLAM with an undersized sand filter hope at the end of the tunnel that it is working. This time it took 4 days before psi was up 5%, 10% after 5 days, then with another vacuum up to 20%+ after 6 days. Tomorrow I expect 25%+ 7 full days since last backwash, up from 3 or 4 days between precious backwashes.
After this backwash I'll add water, let FC drop below 10, drop ph back to 7.2, raise CYA back to 30, then resume the SLAM.
I'm tempted to go higher on the CYA, but maybe I'll wait until it is crystal, passes an OCLT, and CC still less than .5... Then see what I'm losing per day, post it, and gather feedback. No swimmers until it gets warmer, so just tree debris and sun. I'm actually not familiar with a pool that doesn't host swimmers, so this is a new one for me.
- - - Updated - - -
P.S. - thank you to all of you for your patience, attention, and comments. I know I write a lot but I'm hoping it will help future people with similar search terms as far as brown sludge, siphon vac, cloudy, slow sand filter, tree debris, etc.