Final answer:
In this scenario, the EMT should immediately administer the patient's Epi-Pen® as the patient is experiencing severe respiratory distress and has low blood pressure. Epinephrine can counteract the drop in blood pressure and relax bronchial smooth muscles, potentially saving the patient's life.
Step-by-step explanation:
The BEST option for the EMT in this scenario is to immediately administer the patient's Epi-Pen®. The patient is experiencing severe respiratory distress and has a low blood pressure, which are symptoms of anaphylactic shock. Epinephrine, the drug found in the Epi-Pen®, is the recommended treatment for anaphylaxis as it can counteract the drop in blood pressure and relax bronchial smooth muscles, potentially saving the patient's life.