I would like to crossfade two video events, but to keep the audio from the first event during the fade (effectively deleting the audio from the second event for the duration of the fade).
But I'd recommend putting your first video on one video track and your second on a video track above it and partially overlapping it. When you add a Fade In to the upper clip, it will appear as a video dissolve between the clips.
You can then use audio envelopes to manipulate the audio any way you'd like.
Rather than ungrouping, look for the "ignore event grouping" button (looks like a padlock) and turn it on to temporarily disable grouping. Make your individual adjustments to the audio and video tracks. When you're done turn this button off to re-enable grouping. This way you don't end up with the audio & video no longer grouped together.
On my pretty-default setup, it's in the top row of little icons. Find where it says "Make Movie" up there and move to the left five icons. It does NOT look like a padlock IMO, although I can see the resemblance.