[Kuruharan]

While Gollum/Ring are alive, they are bound to one another by despair, to the despair of the world; when they are destroyed, the world's despair is converted to hope. In this sense, I think it is fair to talk about Gollum's despair (which is bound to the Ring) is redeemed by hope when the Ring is destroyed.

But this is not a personal triumph for Gollum. It is a different thing from Boromir and Eowyn. To be quite blunt, I don’t think it is the same thing at all.

Frodo is always being tested by the external force of the Ring

And Gollum isn’t?

For Gollum, Boromir and Eowyn, their struggles really are primarilly, if not wholly, internal as they give in to their own despair and are redeemed of that despair when they find hope again in themselves.

Again, as far as Gollum is concerned, I wholly disagree. You talk about his death with the Ring as being the birth of hope for all of Middle earth, yet that was entirely an accident and not a choice that he made (I also don’t see how the creation of new hope for Middle earth was somehow a great triumph for Gollum). Gollum’s whole will was to reclaim the Ring. That was all that was inside him.

He clearly does wrong in the terms of Arda and his brief, but he isn't anything to do with Unlight

Say what? He abandoned his calling and (incidentally) referred to Sauron as his Master. What exactly are you looking for?