Hm... I can't tell how much but there should be 2-3 arcs before the story ends.
Spoilers (don't ask me details. I just read the short vers from comments in noveupdate)
They became conscious of each feelings a little after this duel/trial. There's an arc about going to a neighboring country for a while this time Shuli and the girl (twin) leaves with Nora. I could be wrong but most romance scenes happened in this arc. At the end of this arc Shuli & Nora became official but this is also the arc where they deal with the Prince. After this there's another arc and this time they fight and confront the Cardinal/Priest & corrupt church (this is also where notorious yandere scene happened). After this arc there's the happy ending. Tho maybe there are extra content/scenes, i don't know of since after the knowing the ending I stopped reading spoilers :/
Thank you PinksNPunks!
*Spoilers*
As for why he abducts her, can't be for anything good. Since he can't control her using any other means, he probably lost it and went mask off. He tried to ruin Neuchwanstein which failed because of Nora and he then poisons Nora, which also fails (and that's when Nora and Shuri get together fr :D)
Shuri does escape though and Richelieu is doomed.
Why are they so hung up in destroying the family? Is it because they're the only vulnerable family? (With no father and all that). Does Richelieu have a one-sided beef with Shuri cos Shuri kinda hinted that she also came back from death (Richelieu said he was basically resurrected but a diff kind unlike Shuri). I'm so tired of them. Just let this family go wtf.
Yep, that's right. He's got this weird obsession with Shuri. She stands out, she's different, she's powerful. I think he's also attracted to her and he thinks she's at fault for him having these feelings for her -_-
PLUS, his twisted desire for her probably makes him think "if I can't have her, no one can, so I'll destroy her."
It's not the Neuchwanstein family he has beef with, it's Shuri's existence.

To getting their happy ending? I've read that they are end game, but how much more bs do they have to deal with before they get their happiness?