I contemplated not commenting at all, but OP is clearly going through it with this boss and will probably be very disappointed after eventually getting through it and realising it was all for nothing. It would save them a lot of time and energy to just abandon the boss and dive in to the manual, which I think is far and away the best part of the game. That’s what I did and I’m so glad. I also don’t know how to convey this to OP without telling them, so it’s buried in spoiler tags which they can choose to read if they want.

You don’t need to beat the final boss to beat the game. In fact, you don’t get the proper ending if you do beat the boss.