First of all, welcome! I'm sorry you needed to find us, but I'm glad you're here
Secondly. I think it's important to know that SPT is only about 50% accurate for positive results (and about 90% accurate for negatives), so that means that it's likely you're not really allergic to everything you tested positive for.
Since you most likely reacted shrimp, I would believe that result as well as the other shellfish results. Since fish is often contaminated with shellfish and vice versa, I would also avoid the fish you tested positive for. As for avoiding all fish, that's something you'll have to decide as you become more familiar with your allergies and develop a comfort zone.
Have you ever reacted to nuts? If not, I'd request an in office food challenge for them.
As for your mystery reaction, what had you eaten in the 4 (or so) hours prior? Could it have been contaminated with fish or shellfish? Nuts? Prepared at home or out? If you can figure out what the most likely culprit was, that will help you in avoidance as well.
As you read here, I'm sure you'll have lots of questions. Feel free to ask away!