Error rates are much higher at the ends. Avoid SCMS if at all possible, by recording to pro decks and dubbing from consumer decks to pro decks rather than vice versa. The 0 VU mark is more critical on DAT than on analog tape, but if your only overloads are very brief percussive transients, let your ears judge. It's much better for the tape. It's bad for the tape, and jams transports.
DAT audio is digital data, and can be corrupted.
If you don't have a second DAT, many hard-disk recording systems have features that allow for backup to DAT, and you can use them for transfers. For critical material, have rotating backups. Label your DATs with track indexes, titles, times, sources, and sampling rates. Keep a notebook if you can. It's easy to lose track of songs.