Kevin, I'm going to add to my suggestion. Those bolt holes just guide the beveled bolts in to where they connect with the beveled part of the front pinion bearing collar making it snug with the retaining edge. They could be loose and the twin bevels do provide a good amount of adjustment. Looking at a different set of notes, the pinion bearing retaining nut is what will limit pinion shaft rearward travel by connecting with the front pinion bearing's inner edge.
If the bearing itself isn't snug it will allow an in/out movement of the pinion shaft, but if it is tight (which will be handled by screwing in the 3 bolts) and if that bearing hasn't failed, I think the pinion bearing nut has become loose. Looking at the digital image of the damage, the pinion is moving backwards by a couple of mm. If the bearing has failed, that could happen and if it is very loose, that could happen but if that retaining nut has gotten loose it would also be a big culprit. Maybe use a piece of wood and a small hammer to tap the pinion gear in as far as it will go and then use an angled piece of metal to try to pull it out toward you. If the bearing is loose, you will see it move (the bearing will be visible through the teeth of the pinion and if it follows the movement of the pinion there's the answer). If the nut is loose or if the bearing has failed, you won't see the outer edge of the bearing move. Hope that makes sense.
