Bench Vise Restoration: Removing Spindle
To get the last jaw screw out try this: choose a short quarter-inch hex bit to match the jaw screw. Place the hex bit into a quarter-inch box-end wrench and close the vise jaws so the bit is trapped and pressing against the stuck screw. Use the box wrench as a handle to turn the bit and loosen the screw. Adjust the vise tension to prevent the bit from slipping.
The pair of holes look small enough to be roll pins or steel pins. They would have the hardness to clinch the groove in the spindle. Poke with a sharp tool, then use a pin punch to tap it out. The holes on the underside look smaller; there may be a step to prevent the pin from falling through. In that case it's probably a solid pin. Punch it through from the smaller hole.