(at around 53 mins) Dexter injects sodium pentothal (sodium thiopentone) into Camilla's key lime pie in order to induce "coma in half a minute" and pancuronium to "stop her breathing". Both these drugs only work that way when given intravenously, and are given only i/v even in general anaesthetic practice. They would not have worked as intended after she takes them orally in the form of pie.
None of the Internal Affairs investigation sub-plot against Deb's partner Quinn makes any sense so far. Amado offered no concrete information on Quinn's alleged crimes, let alone any evidence. All she ever tried was to blatantly browbeat Deb into spying on her colleague. Now, she drops vague hints about him allegedly getting a colleague killed, to guilt her into it. The obvious and logical thing for Deb to do would have been to report all of this to her superior, and a long time ago. This is not even close to the way actual covert IA investigations are conducted.
After Dexter and Rita come home from Miguel's house Rita pours a glass of milk. The name and logo on the milk are for Lucerne brand sold at Safeway stores. Safeway has no stores in Florida.