Thanks a ton. I'm glad you're enjoying it! ^^
It's actually possible to win every fight in the game, even the most ridiculous ones you're not intended to (you probably realized there are many in the game lol). The ch 11 one is the toughest tho xD
There was one guy who managed to deal all of the boss' HP in a single turn, but he had been playing since the first version and was really OP so yeah. I'm thinking of adding a NG+ feature to allow you to replay the game with a more powerful team and get the endings for the quests you couldn't, but no promises yet
The full release (with the last chapter and a bunch of new side quests) should come out in few weeks, so I hope you stick around to that!