Well, it's sort of fixed.
I have reduced the number of units spawning, and I have capped the number of squads each team can have. But that did no good.
Then, I just played around with the sound levels. Not much that just.
So, I went and checked the audio object and change the panning model to Equal Power. Gun shot sounds are still flying Everywhere, but at least it does not hug the speakers to death.
Thanks for trying to help Sushin! This may not be the best solution but it is all I have found so far, and it works well enough for me.