I've made to correlation between the walking stick and the black staff as well. I believe it could be a viable theory. An additionally applicable theory of the missing walking stick is it could be the object Harry has to recover/steal in the next book.

As to Odin being Zeus as well, I find Thor a better candidate for the title or mantle of Zeus/Jupiter. Their both heavily interconnected with lightning for one thing. Additionally Thor becoming Zeus could be Thor setting out on his own. Finding his own place in the world out from under Odin. And Odin/Kringle is mentioned to be an expert in Temporal Dilation in CD which would fit with him being Chronos, Zeus's Father.