FLAC bitrots less than WAV, because WAV doesn't have checksums.
If you're concerned about bitrot (and I feel everyone should be), you're going to checksum at the filesystem level, so it doesn't make a difference
The more the better. Sometimes there's a bit flip on the way to the streaming server…
As someone pointed out above, WAV bitrots results in unreported micro-blips. FLAC bitrot results in reported large-scale failure.
It bitrots at the same rate, but you detect that it happened with FLAC
If your point is that most users of FLAC would be happier with AAC/Opus etc I agree (and with a more significant savings)
And yeah if you're looking at longer archival times, PCM probably makes more sense. But I think FLAC suffers way less rot than, for example WMA