Sounds like you are doing great!

The bleach in large quantities MAY be increasing your pH a bit--even though bleach has high pH the chem action lowers pH to compensate...mostly.

But the dramatic drops in FC mean you aren't out of the woods yet.

Chem_Geek's advice in a nutshell is: With no FC in the water dangerous bacterial contaminants (most seriously fecal matter) aren't killed and can multiply. Keeping the FC up is critical to keeping the water sanitary.

Pond swimming depends on the pond. First off, they are usually far, far bigger, hundreds of thousands or millions of gallons, so a contaminant is far more diluted. Secondly, a pond is an ecological system, a pool is not. The pond has natural mechanisms to deal with biological matter, such as plants and fish, plus it frequently has a constant exchange of water. Also, there is the natural filtering of the ground: Remember, a pond is where the surrounding ground is SO saturated that the water cannot be absorbed--something like 3x the water is in the ground as is in the pond, and that's a filter.

And, the bottom line is: Just how safe IS that pond to swim in?