1. Present items can't get the relationship up to 100. Once you hit their limit, you need either love potions or events to increase the relationship further.
The description for the love potion means that when you use it before the relationship is high enough, it'll actually have a negative effect. Therefore you can't use only love potions.
2. You have to give her another gazer eye to trigger the scene. You can find them in Dorgania or in the Drunken Cave where you find Lace during the main story events.
3. Moriko's events only received the option to avoid harassing her during her events. The choice whether to rape her or not already existed before and was not really changed. If you raped her then you're on her bad path.