JHW: The imperative passage that begins "Pull, pull" continues thru the chorus & into the second stanza. Thus, on your interpretation, the singer must also be asking the Grim Reaper to bear where he goes the words of love, etc. -- not his usual business.

I incline to what I consider the obvious interpretation: That the song is addressed to a generic human being and counsels him or her against despair. If so, then "There's dawn beyond the light" is the right version.

I do have a little trouble parsing the second stanza. I think "affections" should be "affection's". Then it means "Say all that words can say to prove the strength of changeless affection, but keep rowing while you're at it" -- a tall order, but coherent at any rate.