With practice you'll get better at not jumping when your snake strikes, but it's pretty normal.
The BIG thing to remember is that while our snakes are "predators", they too have predators to worry about in nature, and THEY are at risk when they're busy trying to swallow prey. That's why your snake is "shyer" about you watching him eat- it's instinctive, & they'd rather lose the meal they just caught than become a meal themselves for something else that's watching them.
In time, most of our pets learn to feel safe with us around (even when they're eating) but right now it might help to dim the room lights & be as "invisible" as you can; you might also cover his home with a towel, or temporarily tape up some paper on the sides (just newspaper or anything) so he cannot see you while he's trying to eat.
Congrats on getting the first meal into him now- with any luck, it will get easier.Before you know it, you'll be "thinking like a snake" & you'll understand him much better.
And by the way, some snakes (like some of mine) get distracted by me (my motion, nearby) when I feed them too, but it's because they think I'm something to be CHASED as PREY!So "count your blessings" as they say. LOL