idk if you finished and found your answers, but i would gladly give you my own answers that i got from reading the manhwa.
q1: the Empress is doing those things become she needs to eliminate the threat to the crown, because it was mentioned that the power/reputation and standing of the duke can rival the imperial family's power.
q2: the unluckiness came from the fact that the mana flow is unstable, you can even tell that she was already suffering from badluck because of what keeps coming when ian stated living in the villa too, to answer q3: its mentioned by the red dragon that swordmasters are the only ones that can twist their destiny, hence for q4: the destiny of death pointed towards the one person that he was never supposed to meet—laritte. for the last few questions, q2,q3,q4 answers can answer that for you.
hope you had a good read, it's worth it truly.
Thanks for typing all that. I finished it. It's not for me. Q1 always been an obvious one since that position has always been the next powerful title during those times.
The plot and twists did not do anything for me. This is a good read still, gonna recommend it for a short fluffy in the heart type of read (●'◡'●)ノ

why is the empress so hell bent on making his own family, the duke and the duchess suffer? Where did the unluckiness come from? What does it have to do with an overflowing mana from a sword master? Why is only the FL affected by this? What about other ppl close to other swordmasters? Are they experiencing/have they experienced this type of unluckiness?
There's a lot of things i dont understand as the story feels rushed to the point that there are loopholes left open #-.-)
Will i understand these questions once i finish this?