Id say forget re using it, notches too small to take sufficient force , but you could try

a hardened steel Cold Chisel (rather than a screwdriver) and a Hammer , no need to be gentle ..

Or, use a center punch drive the round pin face-race off to let the balls fall out

then put the core in a bench vise and unscrew the wheel from it

get a replacement freewheel with the shimano type large 4 point tool interface