Sorry, but this is wired about as wrong as it's possible to do:\
You're running stereo into balanced line, then splitting the balanced line & hoping to get stereo back. That is not going to happen.
Also you're trying to run a line-level output into a mic-level input. That's going to burn something out if you're not careful.
This is the pinout for the H4n ...
In my experience this is a hardware issue. The sound is when the input hardware of the PC getting too hot signal and clipping. The first step to try then is to decrease the "gain" of the signal going into the PC. There migth be a volume control on the line out or something similar.
A probable better solution is to purchase a simple external sound ...
That won't work. A MIDI output doesn't carry audio. It's used to send control signals between musical instruments ("play note C") and other stage equipment.
What you need is a line-level audio output from the PA system.