He is really very miserable about this, but then, he's really very miserable about almost everything. He's terrified of it happening at all, and disappointed because he caught the implication that they can also control bodies and wanted to test that, that part would be new and easier to verify and have a lot of implications. But he genuinely doesn't think his preferences should get any weight at all so he's not really considering asking her to do more than take a look and leave.
He does have a detailed mental map of Hell, one that might even be useful if they couldn't just conjure it all anyway.
It wasn't much like Angband. It wasn't as bad, and the lies weren't as competent. The place was presented to him as Purgatory, the torment as purifying and exalting. It should have been easy to suspect something, if he'd been thinking straight, but he never really got that chance. There was literally never a moment when he was neither in pain nor at work; they trained him out of even wanting to eat, and tried to do the same with sleep; they kept him desperately lonely and interacted with him mostly to ask things of him. And the things they asked weren't usually horrible - copy books, construct a printing press, scrub the floor, learn new languages - but sometimes they were. Sometimes he was asked to be the one to wield the knife. Sometimes he was asked to take responsibility for the minute details of when and how. He was asked to help teach.
When he got away he cut his tongue out because it was their tool and it didn't even work the first time. He put his eyes out because he couldn't trust them, because he wanted to stop being tempted to believe anything he saw, because gaslighting per se never happened to him other than through sight or hearing (and he thought for a long time about whether he would rather be deaf). He didn't want them back; he didn't parse himself as having a choice; the sense of ownership of his body he was starting to build back shattered when Missut healed him and he doesn't endorse even suggesting that anyone change their behavior in any way over his stupid preferences that were obviously installed by demons on purpose to cause problems, but it feels just a bit silly to be so precious about something he obviously wants and asked for and to just decide to reshape his body on a fucking whim. He thinks it might have taken days to get it all set up stably so he wouldn't just heal. It might be faster now. It wouldn't be nearly as fast as what Missut did, though.
He's exhausted - he still doesn't eat and sleeps even less now, though now he has enough to drink and regular social contact - and he wants so desperately to stop. If ceasing to exist were an option, it'd be a very attractive one. He'd take laying down somewhere comfortable and never moving again, if it seemed like there wasn't anything useful for him to do. He'd take being a yeerk host, probably, if it didn't involve being used for anything he wouldn't endorse and he got along at all with the yeerk. He misses sleep; he has a tendency to have some unholy bastard child of flashbacks and hypnic jerks whenever he tries, and if he waits enough of them out to actually fall asleep he has a tendency to proceed to immediately have horrible nightmares. And then wake up almost immediately. And then have flashbacks about it. He'd take being tortured if it'd convince his stupid half-asleep hindbrain that no one was coming after him.
That's - really most of it, though. Just sheer exhaustion and a little gaslighting that probably did involve illusions but not immersive ones. He was pretty confident about living on Earth right up until he got teleported, a thing demons and no one else he knows of can do and which he was concerned about demons doing to him if they ever found him. He's got a friend and a hobby and a favorite coffee shop.
He's got a lot of languages, so hey, that's something. He'd forget them all in a heartbeat on the principle that things he was taught by demons are probably a negative amount of useful to know, if he could, but he can't.
He thinks it's pathetic to hope for but he's trying and failing not to wonder if Ristrell can tell him that actually it's obvious where all the landmines are and it's fine for him to talk to people and fine for him to take his own preferences into account.