Sky,
Hard as it seems, the half bottle nine hours before T/O is only legal with the 8 hours rule. In other countries a 12 hour rule exists. Some companies insist on a more restrictive rule. "Bottle to throttle" becomes "bottle to check-in" etc. Then it gets subjective - "how much alcohol?"
All that comes to naught, however when a blood alcohol level test is made - which happens more and more these days. There are police data showing how much level to expect so many hours after drinking but the test is the nitty gritty.
Alcohol is excreted via the lungs at a rate dependent upon individual factors. If you can smell the alcohol on the breath of someone, this process is for sure still in progress. If you can't, it still might be.
The only safe advice is to drink no alcohol the night before a flight. This is an enormous change in life style for lots of us. So was learning not to drive home from an evening out on the town but times are changing.