Was Joseph Smith interested in and familiar with Kabbalah? We know that historically Joseph Smith taught himself Hebrew (as to how well, I'm not sure), and that he held beliefs similar to Jewish mysticism (degrees of heaven, preexistence, fall of angels, etc.), but do we know if he had access to and was familiar with Kabbalah writings? Did he study them in the original Hebrew? 

How familiar would the average American Christian leader at that time be with Kabbalah? Is Joseph Smith exceptional in this regard?
In short:


  Do we know if he had access to and was familiar with Kabbalah writings?


There is no documentation of him having access to the Kabbalah writings.


  Did he study them in the original Hebrew?


Again there is no record of Joseph Smith having access to them.

There is a longer article entitled "Everything is Everything": Was Joseph Smith Influenced by the Kabbalah that goes more in depth, but basically says the same thing.


  How familiar would the average American Christian leader at that time be with Kabbalah?


There doesn't seem to be any documentation of American Christian leaders being any more/less familiar with it then current average church leader.


  Is Joseph Smith exceptional in this regard?


If he had knowledge of the Kabbalah then yes he would be more exception than the average American Christian church leader in this regard.

In regards to:


  Joseph Smith taught himself Hebrew (as to how well, I'm not sure)


Joseph Smith started a Hebrew School in Kirtland Ohio and started teaching himself and others Hebrew as best he could. Later he hired a teacher for seven weeks for 320$ (JSHC 2:356) taught by Professor Seixas who did say that the students were 'we were the most forward of any class he ever instructed for the same length of time.' (JSHC 2:396) Joseph Smith later learned more Hebrew (JSP) and German (JSHC 6:426) from his friend Alexander Neibaur. The longer article from above mentions that Alexander did cite the Kabbalah in Times and Seasons in the article 'The Jews' (TS 4:220-22 and TS 5:233-34), but goes on to say he could've cited it from a second source....we don't know.