Hi cgk, since you're going to paint anyway, I'd cut a nice hole in the drywall.
Sometime the fire blocking (that's what you're hitting) is wood a 2x4, yes even with metal studs.
Or it's a piece of metal stud.
Then try to trim enough of the blocking out, to accommodate all the wires you need to run.
It would also be nice to run some flexible conduit in there too. Just for future wiring.
Also, before you patch the drywall, I'd seal the hole you cut in the stud with a spray foam insulation, or a fire proof insulation. Just to maintain the integrity of the fire block.
good luck,
Rick