I cannot comment on 24/30 but most of the video appears to be over-exposed. You are photographing a light source and AE would read the large expanse of darkness in the frame and open up the lens. The camera is set up too low and you seem to be wasting the bottom 20% while some of the bursts are off screen at the top.. I would, if the display went on long enough, try zooming in to fill the screen with those bursts .. realy a hot or miss gamble because I guess you don't know what is planned.
So close down from what AE gave you for this and get in tighter I'm sure if properly exposed your 30 would look great
Never having used AE-lock I would however suggest that it enables you to obtain an exposure and stop it changing as the scene varies. This could be a way to stop the over exposure if you got a tight shot of a bright light similar to the fireworks and then used AE-Lock to lock the aperture that AE wants for that subject matter. If there is some form of EXIF for video shots I would find out what the camera used and then close the aperture down a couple of stops from that ... maybe more after you have checked a short trial run.