There is currently nothing going on between Kung Fu Joe and French Man - it really was a one-time thing.
The boat used in the pirate scene was apparently one of the boats used in Pirates of the Caribbean: The Curse of the Black Pearl (2003), according to Director Glen Berry.
The Hammer that shows up throughout the movie, falling into a dimensional rift, floating in a creek, and hitting The Detective on the head in the end, actually means nothing. This is what was revealed to the audience by Glen Berry on the opening night of Kung Fu Joe at the Pickford Theatre in Bellingham, WA on opening night.