Hey, thanks for trying the demo and I'm glad you like it.
So, this demo is quite old by now and I'm currently in the process of making a new demo with A LOT of changes including changes to the boss.
That being said, you are correct and I agree with pretty much everything you said, many of these things have been fixed / improved upon in the upcoming demo and will continue to be improved upon after that.
So if you find the time to test the new demo whenever it's out (hopefully "soon"), feel free to tell me if you think it's better or not.
Also just to comment on the difficulty spike:
The boss should be easier in the new demo as well and thus reducing this difficulty spike.
But it should still be challenging and dying on the boss now results in less of a penalty as there is a save station closer to the boss.
Anyway, thanks for the feedback. :)