I'll lessen the PC back to 41gr or so and let the barrel copper foul a bit. See what happens then.
Actually, what you really need to do is start over.
According to the 7th edition Hornady manual, the starting charge for IMR4895 in 308Win with 168 grain bullets is 35 GR @ 2100 FPS. Charges are listed as:
35 GR @ 2100 FPS.
36.6 GR @ 2200 FPS.
38.3 GR @ 2300 FPS.
40 GR @ 2400 FPS.
41.5 GR @ 2500 FPS.
43.3 GR @ 2600 FPS, Max load.
If I was starting from scratch with these components, I would probably load 8 rounds each (10 would be better) at 39.5, 40.0, 40.5, 41.0, 41.5, and 42 grains and shoot a group with each to see which shot best. Shoot free recoil from sandbags, make sure you scope is properly parallax free
With a short action the magazine may limit this, but I like to measure the seating depth to the lands, then back off the OAL slightly (~.020" or so). You can also make up test batches with various seating depths to try and determine which your particular rifle likes best, but I have always got acceptable results determining seating depth/OAL this way.
As to cleaning, I clean when accuracy drops off. Depending on the rifle, this can be a long time. I have been on a P-dog hunts where I shot a few hundred rounds with no noticeable drop in accuracy.
Also, how are you cleaning? From the rear with a bore guide I hope, with a good coated one piece cleaning rod. You can wear out a rifle faster with a cleaning rod than shooting.