Speaking of adding a warning, next update, can you add a warning telling us if we're missing anything pre-timeskip before we head into the timeskip?
I understand that that would be nice, but there are hundreds of characters with thousand of events, hundreds of quests, and a bunch of content is optional depending on choices and the order in which you do the events, so it's not a simple task sadly. It would require to go manually through the entire game and search for the triggers of all last events in an event sequence and check what is optional.
If this was made from the start, it wouldn't be as much of a problem, but there is too much content now as that it would be a reasonable way to spend my time.
The CG room, the quest list, and the marriage screen can help you to see what events or scenes you might be missing.