Does it normally get busy on holidays ? Such as Fourth of July ?

Yes on holidays it's crowded. Visit on week days, preferably morning

Yup...

Yes

Best day to go... SUPERBOWL SUNDAY! We went a few years back and there weren't a lot of people.

Holidays is packed....over crowded..best is week days.......mon thru thursday.....

Yes definitely it will be busier. I went there last Saturday and it was still busy. Definitely worth going there. Try going early for parking close to aquarium. Although there is a free MST trolley which takes you to and from the aquarium.

Yes! Later the day it gets less crowdy (1-2 hours before closing)

Yes. Best time to go us around 4.00-4.30pm.