Deadheading is always part of your 16 hour duty day. That is why you can't accept a deadhead flight if it will cause you to exceed 16 hours for that 24 hour period (the company will be forced to put you up in a hotel. *OR* one way around this is for the employee to give up the deadhead with the approval of scheduling, and commute back to domicile. In this case you are NOT DEADHEADING ANYMORE. Why? Because you're not getting paid.)
You CAN be scheduled for more than 8 hours of flying in a 24 hour period... As long as you have no more than 8 hours of flying between rest periods, and your duty day is less than 16 hrs. If, on a day of work you can't fly more than 5 hours because of the 30 in 7 rule, and you're scheduled for 5 hours, you can fly every leg in your schedule no matter how long each leg takes as long as you don't bust the 16 hour duty day.