I ended up using 4mm-width, 30mm length wood screws, i.e. screws with a conical head and a cross shaped recess (for Philips/Posidriv screwdrivers). So, something like the second from the right in this image:
I used a 3.3mm metal drilling bit - narrower than the screw. Since the metal is thin, and likely not very hard, I was expecting to be able to widen the ...
Cut your new patch to a size that would lap the framing halfway.
Lay it in place and trace it.
Cut out the old subfloor to the trace line with your circular saw set to a suitable depth.
While you could add framing blocking, that's sometimes easier said than done in tight areas.
Do you need to seal the faces? Not really in the conditions you described. I have worked in a plywood plant and all the product used the same glue. The difference was the quality of veneer and if any holes were plugged , and later filled and sanded. The last step they did spray the edges and put the company logo on the side of the unit.
Painting the surface ...
If you do not have a table saw and the run out table big enough for this job and you do not have a track saw you can use a straight edge and clamps.
The straight edge (hear after referred to as SE ) needs to be rigid so it will not flex in the middle, a long level works, but some times it so thick that the motor of the saw may not pass over it, and the ...