You are playing at a disadvantage. But if it's low stake and you are mainly there for the "league points", then aggression works.
Play aggressive but mainly against weakness. If you sense weakness, even 72o is a decent hand to reraise. Poker is different than other competitive games where the worst strategy / team NEVER wins; in Poker, 72o will win 20% vs AA. So no matter what, you have a decent backup "get lucky" chance.
Also when you are deep stacked, raise more on the button (obviously); you can often out-play the other guy in position.
In the last 30 minutes before your deadline, if you have to go... Then bully people. All-in festival in town and punish their initial raises. If you are down to 3, their initial raises will be weak, so they are often going to just call you with Ax. Which means you have a good 40% chance even if you are Q8 vs A7 or something equally ridiculous. It takes only a few double-ups to end a tournament.
Not to mention you bought yourself an awesome image for the next tournament... Which means, DO NOT tell them you are leaving early, pretend you are just a maniac players.