Looks like I won't need the pulley boss after all
A friend who works at a local shop let me borrow their drill press & easy outs. I managed to get one of the 4 bolts out without any issues and re-tapped the threads. As for the others, I ended up doing Heli-coils to rebuild the M6x1.0 threads. Everything lines up fine and I tested to make sure the heli-coils hold the bolt torque, so guess I'm good to go.
Since I decided to order a new front cover oil seal that will take some time to arrive, I have one last question. If I temporarily install the pulley bolt now (i.e., torque it down, but don't apply any sealants or thread locker), can I safely remove the 2X4 that is currently flooring the clutch without risking internal engine damage? It's probably not a good idea to leave the clutch floored for up to a week straight. Obviously before I crack that bolt loose again, that clutch will get floored.