Age gaps like this always kill me (like over 5 years). Imagine how painful it would be to lose your lover to old age and having to live decades afterwards alone. Sure it wouldnt be mentioned in the duration of the story, but that is ever present feeling, a subtle dread that makes it hard to love in fear of losing it.
Im not sure why he truly decided to be subsurvient to the idiot dukes daughter, but really he kinda deserved the subsequent imprisonment and torture. He made the decision to serve her knowing what trash they are, he kinda betrayed his friend who was willing to ensure his happiness. He said its cause theyre rivals, but i hope thats not the true reason. If so he deserves the consequences even more. Honestly I would favor him a lot more if this was a ploy and he would attempt to 'neutralize' the dukes family, but seeing how he did seem earnest in serving her that possible redemption seems less likely. Kir, kinda dislike you now, but again happy youre facing consequences of a dumb decision.