My micro-usb was ripped from pcb with copper traces; I glued it back, scratched some solder mask to reveal copper traces, fluxed them and dragged solder from usb pins to traces. It’s so small I can’t really see which contacts are good, but… It does charge (for) now

Probably. Mine has a foam-padded nfc on that cavity, though I could fit a battery below the nfc board. Would have tried but don’t have extra battery handy.

My ripped micro-usb fix is so unstable that it might break any time anyway, so one battery will do

What’s the big white foam suddenly?

You can actually fix the focus more towards infinity by screwing the inner lens part clockwise.