It doesn't really matter which order you do it in, provided you remember to skip the correct turn when the time comes, since you can always use and untap Time Vault at the right time if necessary. I recommend the following, however, to avoid confusion:
Play Final Fortune - you get another turn after this one, and lose at the end of it.
Untap Time Vault - because you skip your next turn to do it, the Final Fortune turn is conveniently skipped, so you don't lose at the end of it.
Tap Time Vault - you get the next turn. Return to top, and repeat.
This has been confirmed on SCG Ask the Judge, incidentally.
I couldn´t find an entry about this in the SCG virual judge, so feel free to link me to that page.
I can´t follow you I´m afraid. You say that it doesn´t matter in which order you take/skip you turns, but 300.6 does.
In your example: play FF, untap vault, tap vault I think you have canceled your own vault turn and will take the FF turn and lose.
Sure you can tap the Vault to prevent that, but in that case you will have to pass the turn to your opponent, with an untapped charged Vault that you actually can´t use until the next turn.
