Battles takes times in Yumi's Dream( I have not tried if changing the speed of battle in options change it much) but there events and walking around that takes time too so yeah the hours go by fast, the last time I played I was over 10 hours but I always check every npc, test every type of monsters, the wind tower takes me about 1h too.
I have no idea how to put a difficult setting in rpg maker, monsters have enough health already as it is, I am not sure yet how I would make things harder, maybe putting again heal skill to monsters that are not bosses or like you say giving some dodge to monsters which is easy to do if I remember right but making them have a "brain" to be more difficult is something I cannot do, I looked into that before and I do not understand how it works (and it would add to the money I spent already)
Proofreading could be nice to fix the mistakes I did( and will do) but rpg maker does not work like Ren'py where I can just save or copy paste all the text, I would need to open every characters text box and write down everything and then doing the same again later for what needs to be changed. Or you mean just for the magic knight Marina story?
So yes you finished the game for now :)
I have not been on Discord for two days but I will check it later today, that would be kind of you to show me how to do, though I am not sure I would understand