Hi,
You asked 2 great questions. What is typical? and How can I help him feel more secure?
Typical behavior for this age includes many fears and concerns as he is figuring our his world. Another writer suggested you write down any concerns you have, as this will help you if you are concerned about the intensity or duration of reactions, and want to discuss it with your pediatrician.
For now, you might choose to do a few things. When he is fearful, be kind, but do not try to "talk him into anything". Matter-of-fact reactions on your part will model appropriate reactions.(Yes, honey, it's a noisy snowblower. Right now it's quiet because it's not turned on.) You may also choose to completely limit t.v. for now. It's rapid rate, in-you-face, graphics and sound are too intense for many children. They are fascinated by it, but cannot internalize what they see and hear peacefully. Finally, security is fostered when life is on a regular schedule, so for now at least, try to keep his day predictable and routine.
Take care