I think both theories have been posted here over the years.. It will be interesting to see what happens now. Actually Alfred might be able to "jail" the Hunger Demon leaving just Thomas minus the parasite.
I would be
very surprised if Alfred can do that.
Someone once asked JB if Mab could remove Thomas' demon. IIRC, JB said something like, yes, she could. She could tear it right out of him. The problem would be that there wouldn't be much left of Thomas when she got done.
The problem seems to be that after that first lethal feeding, the hunger demon and the human soul are more or less grafted together, sort of like a tree graft. There's no sharp dividing line where one stops and the other begins, even though they are not the same entity either. (A grafted tree is physically one organism, but genetically two or more, too.)
Harry sort of saw this in his soulgaze with Thomas back in the day, in the Gaze, he saw human Thomas, the person he
would have been if the parasite had been destroyed in time: not quite so handsome, apparently a bit nearsighted, and struggling with but locked to the demonic entity.
It's that spiritual 'grafting' that makes separating Thomas and the demon (or Lara, or any of them) so hard. If you tear out the demon, you tear out some of the human with it, too. Such a separation would thus need both immense power, and surgical precision, if it's doable at all.