The photos make it hard to see wxsctly what is going on there. But I believe I see a plate screwed to the one side of the gun.

Some of not all of the screws looks to be through the checkering, which is good. Is the plate Inletted into the wood or on the surface?

Maybe a tennon inserted from under the trigger guard to sure up the break and then surface repairs that are hidden by re checkering may work well.

B.Dudley