My mother told me the 10,000 miles away referred to Australia. The boxing glove, just nonsense. How absurd to visit your love with a boxing glove. Think Waltzing Matilda. I do think the kangaroo reference to a shortage of women makes sense. Please tell me my sainted mother was not slyly teaching us about self abuse.
We had a different version about the captain--that "it oft appeared when the gale had cleared that he'd been in his bunk below." I couldn't remember the lead-in to this line, which is why I Googled it, but see no one else seems to have our version. As a child, I loved singing this around the piano with immediate family as well as uncles, aunts, and cousins. There were a number of other nonsense songs in the family's repertoire, some ancient, some not. Apparently, the family has been signing Ol' Crumbles since the days of Cromwell (Ol' Crumbles) and the old woman (the queen). Political satire, of course.