b) Freak transients that cause the other stuff to suddenly become quiet

There's little you can do about that unless you're willing to let the music clip. It could be just one tiny little sample, at too high of a frequency to even be audible. It's the price you pay when using digital compression. I think an analog compressor might allow a transient like that to pass. Wanna write a killer analog-compressor-simulator?

c) High noise floor

What parameter(s) should I be adjusting if I wanted to change the noise floor? I have actually been meaning to play with this, but haven't had the time.

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Tony Fabris