When Finn is holding Lustig on the subway, there is nothing on the floor of the train. When Lustig asks Finn to grab his suitcase for him, there it is on the floor, next to the knife, neither of which were seen in the first shot.
When Arthur Lustig visits Finn, Finn gives him his address as 111 Greenwhich St., which is south of the World Trade Center. The nearest subway stop is the Rector St. 1/9 train. Yet when Finn takes Arthur to the subway, they end up at the J/M/Z Chambers St. stop. When a subway train does come, miraculously it is the G train, which is the only train in the system that does not enter Manhattan at all. In addition, none of the above mentioned trains would take Arthur to JFK, his stated destination, without at least one transfer.
In the scene in which Lustig is shown on TV, the commentator mentions Lustig is due for death by lethal injection. Florida only began offering lethal injection relatively recently. When Finn was a boy, the method would have been the electric chair.
During the beginning sequence where the young Finn is splashing through the shallow water, drawing in his notebook, you can see indentations in the page indicating where the creatures eye is to be drawn