I’m not sure which clock the different RPi3 use.
Commenting out the
arm_freq line will mean you get the normal clock of your pi.
For a 3B that is 1200 and for a 3B+ that is 1400.
If yours is really 800 than i would avoid the -m20
Check your FA stats, MLAT is probably already red.
Btw do you just reboot the pi when you change something like -m20?