Almost lost a wheel
Well, you did over torque them. But I honestly don't think that did it. I tend to agree about the added stress. The farther "out" you go, the more the shear factor. At least that's just my guess. If nothing else, it sounds good. LOL Really glad you weren't hurt.
That doesn't impact the shear load on those lug studs that much, but remember, the longer the spacer, the more
tension is applied to the lug studs. On the factory setup, the shear is transmitted a little bit through the center register and primarily through the clamped face between wheel and disc/drum. If that's too large, a la Magnum 500 wheels, then there still isn't much shear because of the clamp load forcing wheel to drum/disc. Lug studs are primarily a tension device.
Now, picture a wheel spacer that's 3' long. Pushing upwards on the end of that spacer (as in, gravity is pulling the car down) that's a 3' lever
pulling on the lug studs on the bottom, whereas the factory design has that force transmitting basically right up through the face where the wheel and drum/disc meet (which is also almost centered between the wheel bearings). The center of the factory wheel/tire is basically inline with the drum/disc face.
Offset is a thing, for a reason.
Without seeing the fracture face of those studs, it can't be specifically determined what caused them to fail, but I know I'd be calling ARP or someone and replacing all your lug studs.
Then you'll have the right studs for the recommended nuts. :D