OP, the OMM rack is good idea.

You might be able to jury-rig it OK as indicated in #1. Disc brake makes it even more likely that the wheel will become unclamped at some point.

Also, as indicated in #6, this hoop-less style rack is a particularly bad design, as each side has the potential to rotate about the fork leg, moving the pack and/or luggage into the path of the revolving wheel. That's why most front racks of this type have a connecting hoop in the front - so they will not rotate into wheel.

You might want to weigh the cost of a proper rack ($100-200) against the cost of a potential wreck where you could sustain head/face/teeth injuries, in addition to likely bike/luggage damage.