How long should I run my pool filter per day?
This is more of a comment but too long...

I was a pool boy through college.  I have also owned 3 pools.  What you are doing has too many variables.  You have temperature, environment, chlorine levels, quality of original water, amount of swimmers, pump size, plumbing size, pool depth, almost anything around the pool is a variable.

So as a kid I would clean pools, add chemicals and often people had me set up their timers.  But I was a dumb kid and was told 12 hours minimum and 16 hours for bigger pools.  Usually in 2 shifts a day and we tried to set up timer to hours they were not swimming.  

Some customers though set up their own timers and the times were literally all over the place.  I have seen oversized pumps on for 2 x 2 hour shifts and the pool never had an issue (pool was in the middle of a yard not close to house, trees, and wasn't swam in a ton).  I have seen algae grow in a pool that was being pumped 12 hours a day.   

I would think that for your size pool and pump your baseline is 2 x 4 hours.  I would consider 3 x 2.5 hours too.  From there you can work your way down or up as needed.  The big thing is if you are playing with the filter times then you need to keep an eye on the pool.  You have to figure that each hour a day might be $8-15 a month in electric costs.  But at the same time will you have to spend a ton of money on chemicals to fight an algae problem and all the time that goes with that.