A 68-year-old man with a history of benign prostatic hyperplasia and chronic obstructive pulmonary disease presents to the emergency department with acute onset of severe bradycardia (HR 38/min), hypotension (BP 82/54 mmHg), pinpoint pupils, profuse salivation, and bronchospasm with wheezing. His wife reports he accidentally ingested pesticide-contaminated food 2 hours ago. On examination, he has muscle fasciculations and is confused. What is the most appropriate immediate pharmacological intervention?