We’ve looked through your log and found that the load between motors have reduced, this is good.
Regarding further improvement: have you configured PID? If yes, have you run through Autotune procedure without issues?
Also, you’ve mentioned uncommonly high changes in the magnetic field detected by the onboard compass. I also noticed that in your log. Compass readings are highly dependant on throttle. Your motors are creating interference. Have you tried running through compass compensation? This could lower the effect.