As you mentioned with you dad being there, it may have just been due to being out of your comfort zone. Without going into too much theory behind it, the optimal zone of arousal is key in sports such as power lifting. If you became too anxious, then you're less likely to focus on the technical cues. I get this problem all the time with the novices I train, focusing too much on getting psyched up, they neglect the technical aspects. Especially with your opener, you should be focusing on cues and hitting depth and what not.
All I would recommend, is just forget about the meet, and towards the end of your cycle before a meet, make sure you have spotters give commands and what not. You could also get your dad or other significant people in your life to come to the odd session and become familiar with that style of pressure. It's not so much the amount of pressure, just a different kind.
As you do with lifting, your body needs to be exposed to a stimulus to respond and improve. Your mind is exactly the same.