Remember the Monsters? - S8-E12
Plot hole: In order to elude Elway at the airport, Dexter fills a backpack with random items and leaves it unattended under a seat, and then tells a desk clerk that he saw Elway deliberately put the backpack there and walk away, which leads to security detaining Elway and the airport being evacuated. Airports have security cameras everywhere, so security would have reviewed the footage and seen Dexter was the one who placed the bag there. They then would have gone through all security footage since he entered the airport in order to deduce his identity and then located and arrested him.
Remember the Monsters? - S8-E12
Plot hole: A couple episodes prior, Deputy Marshal Clayton stated that he shared Hannah's picture everywhere after receiving a tip that she may be in Miami. In the same episode, Hannah was spotted at a hospital and Clayton was called in about it. This should have only increased public awareness concerning her, but at the beginning of this episode, she somehow made it through airport security and all the way to her gate before spotting Elway and hiding from him in the ladies room.
Are You...? - S7-E1
Plot hole: It's out of character and against his code for Dexter to kill Viktor at the airport. Airports have security cameras everywhere (you can see one on the ceiling when he is wheeling Viktor into the unclaimed baggage storage), and using the unclaimed baggage storage as the kill room is equally unwise, because any airport employee could walk in at anytime and catch him red-handed. Dexter was caught murdering Travis Marshall by Deb just hours before, so if anything, he should be even more cautious.
Answer: No, Harry is not the real father. While he did have an affair with Dexter's biological mother (Laura Moser), this was when she was his C.I. Dexter was already born at that point.