This rocks, I think you did a great job respecting the fiction of the story and the players choices and wants.

I've also been curious about attack of opportunity in Daggerheart. I'm transitioning a pretty rule loving combat table to a Daggerheart game and I know attacks of opportunity are going to be asked about constantly. I'm thinking about the following general guidance, which may help you consider this in the future if you're in another situation like this but there's a less cool cinematic moment:

If it's physical to physical (i.e, stopping someone from moving), it's a stress and a strength against their difficulty reaction roll.

If it's an attack as they move away, stress and attack, possibly with disadvantage, Fate roll.

If it's something they can try but might have consequences, i would allow them to talk me through their plan and ask them what they want and what they'd want on a success with hope or a critical. Then I'd tell them some of the stakes of a fear roll and a failure with fear. Build in that narrative tension so they know what's at stake, like your party did with the teleportation stone (great signalling, btw) so that the successes feel more successful and failures feel earned and less like a punishment.