Those are your best overall measurements since you started this thread. The DO is the most impressive improvement. Not sure what your oil-like film is, maybe something died in your pond or along the watershed? No clue...
Is it safe to assume it has been dry around you lately? If that is the case, then you know your watershed might be the issue?
I have only had minimal inflow since the last readings and, I think you are on to something suspecting the watershed. I was not able to test the inflow because it came overnight and by the time I could get to the pond the inflow had stopped. I estimate that 2/3rds of my 15 acre watershed gets fertilized for hay with some cattle crazing. I can't wait to catch some inflow for testing...Time will tell.
I have questioned the 6.8 DO reading. It was late in the day and I may have written it down wrong. That big of a jump seems unlikely, but the DO levels in the 5 plus range is better at any rate.
I also thought it odd that my pH dipped midday. Shouldn't it peak midday?
QA - FWIW - I have a very similar, if not the same, bubbly film on my pond every morning. Once the wind gets started it seems to clear it up. I asked what it was way back and someone told me proteins in the water.
My films/bubbles act the same way with regards to any wind action. A few calm days at the pond and it gets worse, then some rain and/or wind and it's gone. I suspect the oily aspect is more botanic in nature, (meaning algae blooms), but there could be some organics in play.