I 100000% agree with feeding within the enclosure. My King has a pretty insane feeding response regardless of season but has never even lunged at me inside his enclosure. He's an adult and over 4 ft and 675 grams and will occasionally, though very rarely, rattle when I reach for him. I just leave him alone those days. I handle him usually 4 -5 days a week for anywhere from 10 minutes to an hour. He was out tonight for about 45 minutes and was chill as can be the whole time.
Every animal is different, but most Kings chill out pretty well once they get a little more size and confidence. I say just keep doing what you're doing and you'll be fine.
I also agree with washing your hands and forearms before handling any snake. Coincidentally, I like lemon scent so usually use that.