In short -
(1) don't check bags. Bags will go through to TPA.
(2) technically against the rules, people do it all the time. for some, it's gaming the fare, for others, it's because plans change mid-flight. don't make a habit of it. you won't get miles for the flight you do not take.
(3) in the event something screws up, DL's only obligation is to get you to TPA. They could route you through DTW or any other hub. I personally know someone that got screwed by this when doing something similar on another airline.