This doesn't make sense but I've heard it several times before. Wheel studs in good shape should not snap at 109#. The OEM steelies are the "stock" wheel; the alloys are an "option." The steelies torque at #110 (IIRC) So why would the studs not be able to handle this torque regardless of which wheel is being used?
For the record, I am NOT suggesting anyone torque alloys beyond spec (76# in my case.)
Definitely buy a bigger one, most measuring devices are inaccurate at their extreme ranges. You must be using a 3/8" drive, you'll be much happier with the extra leverage of a 1/2" wrench anyway.