(Sorry for resurrecting this. Thought some people would like to know the progress)
FYI I ended up digging out the 2 holes by hand. I dumped a bag of concrete in the bottom of the holes and filled them with sodium bentonite the rest of the way (I used about 10- 80lb bags.
It filled up right after that. It's definitely holding *better* now but it still has a slow leak. It still hasn't filled up all the way.
It has dropped about 4ft since it's highest in January. We haven't had a lot of rain
I spread 180lbs of soilfloc around the area of the suspected leak 2 days ago. Now we wait again
Current photo