@KekuZ3ref i would recommend just doing your own pace on the amount of chapters for 'for you', no need to set a limit on how many chapters it should have (this statement might not be that helpful for the specific amount that you are asking for, apologies for that)
The ending is kinda tough because i could somehow see the story ending in either bittersweet,horror type or just full on romantic end for both sakusa and y/n, (for my personal preference i just hope the book wouldn't have a sakusa is keeping y/n captive in his house/basement and stuff i just somehow dislike it when books goes in that direction, but if this book does i respect the decision and i just know you guys would make it interesting and good to read because these clichés in yandere fics are hard to pull off)
a great thing i enjoy about this book is the way you write sakusa its just *chefs kiss* and i really have no complaints on the pacing of the book its just fine for me and i swear its not slow
and I would love to read other works from you guys, hope this somehow helps and just take your time to find inspirations