There is a video covering a set up for a Kenwood TS-590s.
That radio has an internal USB audio CODEC and serial port for CAT, the same as the IC-7300.
Take a look at that and see if it helps with your audio.
There are also a couple of guides that include settings for the IC-7300 settings here:
Check on page 8 for the IC-7300 settings.
73 - Mark - K8MHW
'A RigPi Enthusiast!' - I am not otherwise affiliated with MFJ or RigPi