Terrific overview!
Just one correction. You say about Jin that His lack of money during the series indicates that said family cut him off. But in fact, any lack of funds he has at the start is directly the result of him being on the run after killing his dojo master.

Other than that, this is really, really well done. And as you point out, the three characters - and many of the minor characters - can be put together in any number of romantic couplings!