There exist two wonderful books by Charles Earle Funk. One is called "A Hog On Ice & Other Curious Expressions". The other is "Heavens To Betsy & Other Curious Sayings". Both are well worth the $8 (U.S.) each to keep around for just such questions as these.

Regarding Sam Hill, he says this:
"After long an diligent search for some American of sufficient prominence in a bygone generation to justify the continued use of his name, even to the present time, in such sayings as 'to run like Sam Hill,' 'What the Sam Hill,' 'Who the Sam Hill,' and so on, I have come to the conclusion that the editors of the 'Dictionary of Americanisms' were right in calling the term 'a euphemism for hell.' It may be, as Edwin V. Mitchell says in his 'Encyclopedia of American Politics' (1946), that there was a Colonel Samuel Hill of Guilford, Connecticut, who continuously ran for and was elected to public office in both town and state, but this colonel, though perhaps locally prominent, does not turn up in any of the numerous biographical records I have consulted. Nor does Mr Mitchell supply any dates. The expression itself had sufficiently widespread usage to extend into Schuyler County, New York, by 1839."

He obviously didn't become aware of the Washington Sam Hill mentioned above or else the date of the Schuyler County appearance may have predated that railroad magnate. I'm sure I don't know.

John Brown was hanged. I imagine the expression phrased in the post above was a euphemism for "I'll be hanged!".

Mr. Funk has this to say about Jack Robinson:
"This means in a couple of shakes, two shakes of a lamb's tail, or, in plain English, immediately, with no loss of time. The expression arose during the latter part of the eighteenth century and, as far as anyone has been able to discover, it was no more than a meaningless phrase. No 'Jack Robinson' nor 'John Robinson' attained any prominence at that period.

As to the meaning of "swan" while I have always thought that it was used instead of "swear", I remember reading a discussion somewhere in which someone offered the idea that it may have come from the word, "swoon" which, besides being defined as losing consciousness is also said to mean being in a state of bewilderment. I don't have any answers for this one but thought you might find those possibilities of interest.