The quest is broken for me right now because Benryn won't get up at all (no matter what option, pass or fail checks). It's been a bit wonky the last 2 patches, honestly.
I encountered the same thing. What I discovered was that even though he didn't get up, the game seemed to think he had and so didn't burn him. So my solution was to leave after freeing him, fast travel away, long rest and fast travel back. I found him where he was supposed to be, kneeling over his wife's body (I reached him by going in through the side building, not the front btw, so I don't know where he goes if you come from the front building). Cue quest progress as normal.
It is an annoying quest, though, both because of that bug and by poor mechanical design. I could only talk to him without us both roasting to begin with by entering turn-based mode before breaking in the door and talking to him. The fire spreads
way too fast otherwise.
