Well, your description of the game is fair. I didn't think the fans were all that bad. Irmo seems to be about on the same level on a normal basis.
Shots:
Irmo 13-6 (first half 8-1, pretty dominate)
The second goal was not clearly offsides. I (like you) was watching the ball as it was played, and when i looked where the ball ended up, the player was off, but I don't know where he was when the ball was played. The linesman was certainly in perfect position to know, and therefore I'll go with his call every time.
The second half was much more even, and Greenbriar had their moments where they had their way in the midfield. Irmo had alot of opportunities in both halves, but they seemed to play with negative urgency, especially when they were down by 2, taking ill-advised shots and what not. Prince's header that went just wide in the first half looked to be a goal for sure.