Welcome to KIC first of all!
1. It probably won't be as packed as a weekend but seeing as it's late on a Friday I would guess more people would be there as compared to a normal weekday. You probably won't have to wait more than 45 minutes, really that's just for Firehawk. The rest you would probably have a maximum of 20 minutes to wait.
2. Firehawk is a must and is definitely worth the wait. Son of Beast is a pretty sweet ride as well. It will probably have a half hour wait. If you do only two things make it them. Top Gun (Flight Deck) is fun but definitely not a must. However, there is hardly a wait for it, so just go for it. Try to get the very front as it's the best seat.
3. I think you'll have more than enough time to make it to all the rides you want. Beast doesn't really pull gigantic lines, you'll probably end up waiting 20 minutes max. I would say hit The Beast last as the darker it gets outside, the more you'll enjoy your ride.
After The Beast go to X-Base and hit FoF and Firehawk. After that head for all the Action Zone rides such as SOB, Invertigo, Drop Tower, and Flight Deck.
And don't forget to end your day with a nice blueberry ice cream.
Have fun!!