Yikes! I'd get some steel bars and flop and chop 'em.

Looking at the pic, it looks like the top right stem clamp bolt is WAY more clamped than the top left. This is not good. You need to slowly screw each one in a bit at a time using a pattern. Top left, bottom right, bottom left, top right. Repeat that pattern often. Don't let one bolt get too far ahead of the others. Get a torque wrench.

Not sure if that's what caused this failure but it's not good.