How to disable autofocus and set focus to infinity?
I'm sure there's some way technically to simply shut off the autofocus, making the camera start up in a default focus and never moving away from that. It is however not a function that I am aware of that it exists in custom ROMS, because that's the only place you'll find modifications like this, and unless there's a big demand for it, it's unlikely someone will code it. I've got a feeling that camera focus might be really tricky to mod from the actual OS.

I think the only way you'll solve this for sure is basically learning to code and inspecting the AOSP source, or paying a developer to do it for you. I'm almost certain it's not a native function of the Android OS.