Looking at that closely, the whole corner has been seperated ( hence the wood screw )
I would have started by taking that out and slightly open the joint then lots of wood glue and clamp for a few days.
After dry, I would have tried to build up the rest with epoxy or fiberglass making a mold to hold it in place. Then a rough sanding building up again if needed to make level.
I would have finished off with green glazing or spot puddy to get out any imperfections. Lots of sanding and eyeball work to make perfect.
Mask off artwork and spray with primer and flat black fading into the original.