Sometimes it's easy to forget how sinister Twilight can be. Or at least how sinister he used to be before he slowly settled into his family man persona.
Aside from his initial attitude toward Anya ("when this mission is over she's going straight back to the orphanage"), he also planned to coerce/seduce/con Yor into marrying him within one week.
"First I get her to take on this small favor, but by the end I'll make her agree to get legally married."
Of course Yor surprised him by proposing first, so we never got to see that dark path emerge.
...Except actually we sort of did. Twilight did try to go down that dark path briefly in Chapter 35, but Yor knocked him out and made him think she had no romantic interest in him. If she hadn't done that...it's sad to think about what would have happened (as @katzennstack wrote here).
Fast forward to the mole arc:
Instead of manipulating Yor for his benefit, he nearly lost his life to protect her from getting hurt (emotionally). Several months of living with Yor and subconsciously admiring her strength and kindness had indeed made him "lose his edge" as he sort of mentioned to Nightfall.
If another family crisis had emerged, would he still have tried to coerce/seduce her into staying in the marriage at that point? Unclear. But his decision to spare Yuri seems to indicate he would have hesitated a lot.
Fast forward again to when Yor comes to terms with her feelings:
Instead of seeking to trap her, he thought, "If...Yor insists she wants to be freed from our agreement, I'll have to respect--" before he cut himself off and his thoughts went to Plan C. But before all the rationalizing, as others have pointed out, his emotional reaction occurred first. He looked just as terrified/shaken as in the mole arc when he thought the SSS had gotten the jump on him (but it turned out to be a WISE colleague):
He may still be willing to go to extremes like tranquilize Yor just to escape an SSS party, but to cause her lasting harm like he'd initially been willing to...I think not. Seems like he's subconsciously locked into "How can I minimize the amount of harm I'm inflicting on Yor and Anya" while continuing to carry out his mission.
Except at some point, like in many fanfics, he may crash into the reality of how much he's inevitably going to hurt them when the mission ends and he has to leave/"die", or they find out he's been deceiving them the whole time. Will that be part of the next Twilight spiral?
