Okay, so for some reason restarting the system without memory card and putting back again fixed it. It scared me enough, so I just switched back to retail mode using the idu HENkaku app.
For some reason though, my apps' background was grey. Rebuilding the database fixed that.
Although, I'm kinda surprised. Why did this happen exactly? I searched a little, and apparently no one ever had this kind of problem bricked while just editing app.db. Does anyone know if it's because I tried to add the package installer, because I was in IDU mode, or both?