[burrahobbit]

in Gollum we see a creature beset with failings so unimaginable, we can see there is no hope for him

How inimitably rude you are to him.

Tolkien:

If we speak last of the "folly" of Manwe and the weakness and unwariness of the Valar, let us beware how we judge. In the histories, indeed, we may be amazed and grieved to read how (seemingly) Melkor deceived and cozened others, and how even Manwe appears at times almost a simpleton compared with him: as if a kind but unwise father were treating a wayward child who would assuredly in time perceive the error of his ways. Whereas we, looking on and knowing the outcome, see now that Melkor knew well the error of his ways, but was fixed in them by hate and pride beyond return. He could read the mind of Manwe, for the door was open; but his own mind was false and even if the door seemed open, there were doors of iron within closed for ever.
How otherwise would you have it? Should Manwe and the Valar meet secrecy with subterfuge, treachery with falsehood, lies with more lies? If Melkor would usurp their rights, should they deny his? Can hate overcome hate? Nay, Manwe was wiser; or being ever open to Eru he did His will, which is more than wisdom. He was ever open because he had nothing to conceal, no thought that it was harmful for any to know, if they could comprehend it. Indeed Melkor knew his will without questioning it; and he knew that Manwe was bound by the commands and injunctions of Eru, and would do this or abstain from that in accordance with them, always, even knowing that Melkor would break them as it suited his purpose. Thus the merciless will ever count on mercy, and the liars make use of truth; for if mercy and truth are withheld from the cruel and the lying, they have ceased to be honoured.

Melkor had the right to exist, and the right to act and use his powers. Manwe had the authority to rule and to order the world, so far as he could, for the well-being of the Eruhíni; but if Melkor would repent and return to the allegiance of Eru, he must be given his freedom again. He could not be enslaved, or denied his part. The office of the Elder King was to retain all his subjects in the allegiance of Eru, or to bring them back to it, and in that allegiance to leave them free.

Tolien says that The King Of All Naughtiness can make it, I'm pretty sure that applies to little worm things too.

P.S. Worm things don't need to be alive to repent, cf. Elves in Mandos. Now you are saying, but wait a minute, worm things are not Elves, that is a stupid comparison. I don't care, Beren did it too, and he is the same sort of thing as a worm thing. And that sort of thing gets to leave the confines of the world when it dies, no matter what. Tolkien said so. What Tolkien says is right and what you say is wrong.