I have always sung the full 5 verses: I can work with the contrast between verses 1,2,4,5 and the angry verse 3. If you look back at my post from 2009, I did mention that one band left verse 3 out, much to my consternation! I do go loud and angry in v3 and then quieten down again in v4. Each to their own, I suppose. I don't have a Scots accent, although had a Scottish mother, so I do have to work on the pronunciation, although this particular song has less of the broad Scots in it than some of Burns' poems.
I have always sung it to the tune popularised by Dick Gaughan, which has a range of an octave + 1 tone, so not too much of a stretch. I did look at the Port Gordon tune, but it also has a range of an octave-and-a-half a seemed a particularly miserable tune to me, so haven't gone any further with that.