To answer your other question, you definitely shouldn’t need different calibration numbers for customs in general as opposed to official content. However, specific songs could be poorly synced to the audio. Do you have an example?
Just about every Dream Theater and Mastodon song is off, but by varying degrees. The worst is Assassin by Muse. I can play guitar just fine after calibrating, but I can’t hit a single note on drums. I don’t know why such a discrepancy exists between the two instruments.
