Nobody so far is addressing your problem from this angle, but normal torque values 1/2" Fine Gr 8 are 90 ft/bs. I am not sure how one can relate removal torgue to tightening torque. It seems most are assuming they are the same, I'd want something to back that up. Further, the conical dry wheel hole seat, has got to significantly distort measured torque vales when tightening. And this all leads to the premise, wheels are meant to be secured to the mounting surface by the induced friction of 5 properly tightened fasteners of the necessary capacity for job. Shear resistance is not supposed to be a concern. And 5/8" studs allow typically double the torque values, with a corresponding increase in friction from the clamping they supply. I think being distracted by the centering concerns/hole design is not solving the real problem here.

On drilling out conical wheels to fit larger 5/8" studs, I would hesitate, I believe one aspect of the typical conical seat design is, it allows for a slight amount of give and tension to be applied and maintained thru use and temp, etc variations, kinda like a large circular lock washer, one of the reasons on steel wheels the metal directly behind the conical seat is not designed/intended to bottom out on the axle flange, but keep a space. With 5/8" larger studs, the metal is compressed greater, into a range a 1/2" stud could not approach, but wheel hub is the same thickness. Not sure this is ideal solution, if wheels weren't ever offered in the larger stud sizes.

I'd like to see the backside hub of the OP's steel wheels.