Congrats! First time is the hardest. If you think you'd make more money being personally able to move around the room you can consider paying someone to be the main "day of" person. With our Berkeley show Wormboy and I put it on but during the day of, he's the main guy in charge so I can sell, etc.
As for it slowing down by 2 pm, that's not too surprising. I wasn't sure it would happen with your show since there would be a lot of dealer to dealer sales, but most one-day shows I do, it slows by 3 pm, so that's only an hour difference. For our Berkeley show I wanted to avoid that for the vendors, so we made it a tight 5 hour show and the first time it didn't die until one hour to go and last time, 30 minutes to go. As our crowds grow we'll have to start extending the hours to thin out the crowds a bit.
Again, this is a great start you've made.