I had to shut down my computer during halftime, will this affect my statistics recorded in the 2nd half?

No. All actions are saved immediately in the local database – you will lose nothing. Once you have re-booted your computer and opened the GameTime form, all display fields will be recalculated. The game time clock will be set to the time of the latest statistic. For example, if the last game statistic was a ground ball with 5 seconds left in Period 2, then the game clock will show that time. If needed, run down the game clock to the end of the period or manually set the period and the time.