You would expect a small Boston theatre that presents edgy works to be struggling as funding goes down. But the enterprising SpeakEasy Stage Company found itself unexpectedly blessed when “an improbable musical comedy about a charismatic but bloodthirsty freak of nature who longs to be a normal boy” sold so well earlier this season that the company brought it back for a second run. Its success at the box office has put the company in the black.