By how much can video and audio be out of sync?
There are, in fact, several standards on audio/video or lip sync. The problem is, they can't all agree on what the acceptable error is. What is well understood is that if the audio lags the video it is less noticeable, because that is natural. Something that is further away will be seen before it is heard. In the list below, a negative number is the audio lagging the video and positive is the audio leading the video.

ATSC IS-191: -45ms to 15ms
EBU R37-2007: -60ms to 40ms
ITU BT.1359-1: -125ms to 45ms
ITU BR.265-9: -22ms to 22ms

ITU BT.1359 was based off studies done with average viewers, but relied on significantly older technology. The ATSC and EBU recommendations rely on expert opinions. The methodologies don't give you a hint at which one is right. I've worked at facilities that used -2 frames to 1 frame (roughly -33ms to 16ms at 60fps) as an easy to remember guideline with very few viewer complaints about lip sync.
Even with the disagreement, 0.1s (100ms) of error will almost always be noticeable, unfortunately.