If you're shaking and splashing around a ten gallon fermenter, then there is no possible way to get too much oxygen in your wort. The only way to get too much oxygen in wort, is to use an oxygen tank and pump pure O2 into your wort. When you put pure O2 in with a diffuser stone, then you can get too much. If you use an aquarium pump with a diffuser stone (which is putting regular atmospheric air in the form of ... by volume, dry air contains 78.09% nitrogen, 20.95% oxygen,[1] 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases.), you can't get too much oxygen.
•Shaking/Agitation/Splashing for 40 seconds = 8 ppm max
•Aquarium pump with a diffusion stone for 5 min (using air, which is 20.95% oxygen) = 8 ppm max
•Pure oxygen in a pressurized tank with a diffusion stone for 60 seconds = 0-26 ppm
While most yeast strains have individual oxygen requirements, the average amount needed for a healthy fermentation (SG < 1.065) is between 7 to 18 ppm (around 10 ppm). With pure O2, you can get up to 26 ppm.
Yeast use all availible oxygen in the first 3-9 hours. As long as you are doing a 1 or 2 time dose and are not running pure oxygen on a continuous basis, there is no real danger of over-oxygenating, only under-oxygenating.
You don't really say how you're adding your oxygen with the 10 gallon batches. If you're using pure O2, then you could be over-oxygenating. If you're still trying to manhandle 10 gallons to splash it around, then your issue is not over-oxygenation.
How long do you pump regular air or O2 is as follows:
An apparatus diffusing air into chilled (< 70 °F/21 °C) wort typically needs to run for a minimum of 15 minutes to achieve adequate oxygenation, where the same set-up using pure oxygen would require only a minute or two at the most to achieve the same result.
I hope that you found this helpful.