Her mine of rubies also guarantees she has her own money. She will never have to feel indebted and ruin the lovely dynamic they have now. Hate when that happens. She can pull her own weight.
Yeah, ML have no interest for the throne. But because he is direct sibling to his sister who is a strong candidate for the throne, his life is always in danger since he can always be used as hostage to bring down his sister.
So, he is trying to go back to the castle to reduce problem for his sister to not worry her. Once his sister got the throne, ML intended to go back to the forest with MC, because he said he feels more at ease there, like that way of living is more preferable for him.
Or hope for how the story will end: am I mistaken in remembering that Leon returned to help his sister and not take the crown for himself? The author has always been unconventional in presenting gender roles here so I think the sister will get the throne, do a bloody swell job at it, and ML will live out his days happily with Aria who will become a titled lord or somethin.