I've got a leak also. We've had very little rain since the first of the year, and I'm down 30". We did have 2" of rain a few weeks ago, but very little runoff.
I've bought some of the soilfloc, but haven't applied it yet. I've heard hydraulic pressure will help it, so I was waiting for it to fill from some big rains, but we aren't getting any.
Then I heard get it down before all the FA covers the bottom, but I don't think I've got that problem. I do have a fair amount of leaves on the bottom, as my pond it tucked into the trees. I guess what I've come to think is, put down the soilfloc, or whatever sealant you are using, when ever you can get it done. I'm trying to line up a little help, at least one additional person to help line up the grid, and pull the boat across.
As long as the wind isn't too strong, I'm going to go for it.
There are so many variables that affect the leak rates (you mentioned most) that measuring it and tracking it, seem a little pointless.
Just my $.02..
Jeff

12 yr old pond, 1 ac, 15' deep.
RES, YP, GS, FHM (no longer), HBG (decreasing), SMB, and HSB (only two have been seen in 5 yrs)
I think that's about all I should put in my little pond.
Otter attack in 2023.