Okay. Start with what he knows. Might know. There's...nonzero evidence here that actually he's still in the situation where he can't know anything ever again. But it's not like he was absolutely sure before. Just...sure enough.
How much does this change that. Is he still sure enough.
It's been a subjective year. Or - he thought so, at the time. He has - had - a year's worth of notes to prove it, but not here. A lot of events happened and he's pretty sure he remembers them, along with a lot of very samey days and nights that are nonetheless stubbornly seared into his memory, he was hoping that would eventually make the things that came before this past year less salient.
If Melkor had figured out how to replicate compulsions and Mindhealing, the war would've been over in a week. It's...not impossible, that everything since then was some sort of elaborate game, but - it's not the sort of explanation that actually leaves him less confused?
He is not, currently, being tortured. The situation was baffling and scary but - not in a very targeted-at-him way? Plausibly it was less frightening for him than it would have been for, say, Herald Dara? It's, in a way, more surreal and confusing than frightening.
Also he's not being asked to do any magic, and he couldn't anyway.
Fine. Start with that.
If glowing-woman asks him to do magic, or anything else that could have genuine significant effects on the world, he'll refuse and update his probability estimate of still-in-Angband. (On reflection, helping her collect bones was...probably still okay? She was already doing it, he just made the process 20% faster, and he was the one who offered at all.)
As soon as he has more downtime, he'll check his memories of the last year, make sure they actually do contain a year's worth of real details.
In the meantime, he will - hold his beliefs about what's happening lightly, but will continue to act on the assumption that this is real and worth updating on.