"鐵釘或膠枝 點樣可以固定? 要鑽穿多少少再放入長既鐵釘或膠枝?"
You can 鑽 a hole in each side of the broken pieces. Put a 鐵枝 inside as support to connect the 2 pieces and stick with AA膠.
But I don't know if it is ok, if the body is too heavy.
Your one is repainted version.
It is not so old, why is it so fragile.
BTW, that part looks plastic to me.
I would try to use a clamp to pull the broken part out. Then I will use some screw like those used in Studio Half Eyes to re connect the broken parts together. Finally, I will add AA in between them.