He's just beautiful and is doing so well! Please don't slow down with photos and updates.
Given that you have to remove the whole door for feeding time, I wonder if it might reduce the surprise/stress of doing so by signaling in advance that it'll be happening - something like three taps on the door, then waiting a minute, then removing the door, maybe?
I have to say I don't think you are being too cautious at all about the door. If he can shove his nose through the gap, he can shove the rest of himself through. It's really astounding to see how small a space that a determined, curious snake can get through if they put their mind to it. This is why I don't have sliding panels on my enclosures, but I know they can be made secure.
For what it's worth, I've kept snakes for a long time and I think it's fair to say I am still a helicopter parent.