I actually think keeping her from the truth was the way to go. How would Mirai ever trust Mutsu if she had disclosed that they were the ones who took Yoshie away from her? Would you really trust that a person who went through with doing such a vile procedure to someone close enough to you that...
This chapter is just plain stupid, "I'm going to arbitarily set my prices according to my personal biases" is such a childish interpretation of "fairness".
We don't know yet, but I'm guessing rather than Lucius himself remembering past Revolve timelines, it's the demon king relaying info, as Chapter 49 mentions that the demon king appears to have gained the ability to remember Revolve timelines after Albus used Retrograde on him.
From the Guild Master's interaction with the noble's messengers, it appears that nobility outrank the adventurer's guild in general, so she's stuck there unless she wants to risk total war.
If a seemingly innocent and harmless individual suddenly appears in a dangerous place and reveals herself to be aligned with the enemy, I'd be very worried about said individual being more than what they seem.
That's the point, they broke up out of circumstances rather than the relationship falling apart. They're both still in love with each other and so they're both reluctant about moving on despite having to.