It is impossible to track the lot number of a prescription drug with no information as to when and by what pharmacy it was filled. Also, Agent Park has no pharmaceutical experience and could not possibly identify a random small, blue pill that quickly.
Ressler tells the task force that Sweeney lost the special election. The election was called because Sweeney was missing, presumed dead. Why would his name be on the ballot?
Near the end, the two F.B.I. agents have the gun criminal at gunpoint. She has pulled, has the hammer cocked, and is directly threatening an unarmed captive. Neither agent fires their gun, they just stand there and watch her execute the captive. Law enforcement, which includes F.B.I. agents can use deadly force to stop the use of deadly force against themselves or another. Their failure to act would result in both disciplinary action (censure) as well as a civil suit.
Rostova's MI6 contact speaks a comically over-the-top parody of British English. It makes him sound like Austin Powers without the double entendres.
It makes no sense that Reddington should still be unawares of who moved in next to Liz. It's been weeks and months. He is a controlling personality who has been obsessively keeping tabs on Liz. With Liz' new-found appreciation of him, she would probably have told him about her herself. Earlier, she even involved him in picking out a nanny.