Lossless volume control:
MP3GainGeneral/lossy editing:
AudacityLossless editing:
mp3DirectCutGeneral media conversion 1:
MediaCoderGeneral media conversion 2:
SUPER - note the download link is hard to find.
Video editor:
Avidemuxthese are all the media editors I use on a frequent basis. Mediacoder to convert files, avidemux to re-encode/crop, but what you're looking for is audacity, since wavs are lossless. Anything you do in audacity to a wav file is essentially lossless.
Also, can't you just reduce the volume with a timing section?