There’s not a whole lot you can do.
Turning it down won’t help… Turning down the audio in the digital file isn’t any different from turning-down the playback volume… Turning-down volume doesn’t remove distortion that’s already in the recording… You can’t remove distortion.
Try the Equalization effect. If you are not familiar with equalizers, the bass is on the left and the high frequencies are on the right. i.e. Boosting the high frequencies will tend to bring-out the cymbals and the “T” and “S” sounds for more vocal clarity (if that’s needed). When you’re experimenting like this, I recommend using the equalizer in the Graphic EQ mode.
the drums are too loud.
You can’t really isolate the drums. The equalizer can possibly help, but there is a lot of frequency-overlap between all of the instruments and vocals. You can try the Compressor effect. Dynamic compression boosts the loud sounds and/or reduces the loud sounds, so it tends to bring everything toward the same volume.
But… [u]Clipping[/u] (overload distortion) is a kind (the worst kind) of dynamic compression, since the peaks are limited, so the recording may have a lot of compression already.
NOTE - After applying EQ (equalization) or doing anything that might boost the volume, it’s a good idea to run the Amplify to bring the peaks back down to 0dB (if necessary) before exporting the audio. Audacity itself can go over 0dB, but 0dB is considered the “digital maximum” and some file formats will clip at 0dB. (Even if the file is already clipped, you don’t want to add more clipping.)
I’ve extracted the audio using VLC so I can work on the audio alone and then add it back in later.
I’m not sure, but as far as I know VLC can’t re-multiplex the audio & video. You may need a video editor for that. I use Corel Video Studio, but maybe you can find something free if VLC won’t do it.
It’s difficult to record live amplified music. Pros do it by close-micing all of the instruments & vocals (and they record multi-track with each mic on it’s own track for post-production mixing).
You can-get away with multiple mics and live-mixing while recording in stereo, or you can even tap-into the PA mixer. But the PA mixer only has a “good mix” when ALL of the sound is going through the PA system, and that’s usually not the case at small & medium size venues. …And, if you’re playing an stadium or arena with everything pipped through the PA, you’ve probably got the budget for full multi-tracking.
Acoustic music is a lot easier. You can usually get a good recording with a pair of stereo mics at about the same distance as the conductor (or where the conductor would be).
At the normal audience listening position, you usually get far too much room-sound (reverb and noise). …The amount of reverb that sounds great in a large music hall usually sounds bad when coming from a pair of speakers in your living room.
And for any recording, of course it helps to have reasonably-good mics into a reasonably-good interface, or a solid-state recorder. Or, there are some [u]special purpose microphones[/u] that can turn an iPhone into a solid-state recorder.