In our shop I would remove the metal. Test if there is any way to flex the crack, perhaps pushing down on it or pushing the sides out. It's better if you can flex it, but I suspect pushing down is the only way you'll find that works. Next brush acetone on the crack area, trying to clean out the oil. Now put a 100 watt lamp right over the area, until it is hot; might take about 30 minutes. When it's hot, leave the lamp and mix a two part epoxy, like acraglass. Leave the fiberglass flock out of the mix. When epoxy is ready you can brush the crack again with the acetone, then put some epoxy onto the crack area. We usually see the epoxy wick right down into the crack and so we apply more. If the crack can be flexed do that while adding the epoxy. If the cracks won't flex at all you can add a drop or two of acetone to the epoxy before putting epoxy in the crack - acetone is an epoxy thinner and will help it get further down into the crack.

clamp the wood down, or wrap rubber bands around the section to clamp it. when using clamps I put a piece of plastic on top of the glued wood and clamp over that to avoid gluing clamp to the gun.

After epoxy dries (next day) you will need to clean out the epoxy that ouzed into the tang space. If you prefer you can coat the tang and screw with epoxy release and put them back in during the gluing. I would probably just glue the cracks and not let too much epoxy run down into the tang cavity. Sometimes I would make a fake tang for a piece of wood, then coat with release agent or wrap with plastic and clamp that into the cavity.

You will have to use coloring agent and re-inlet the tang if it wasn't in the gun during the repair. Whether you left the tang in or clean out the cavity you should use inletting blue to check the tang placement after the job is done. You want to check that the tang does not touch the rear of the cavity to prevent the stock from being cracked again.