Thanks for the comment! I agree with you on pretty much everything you mentioned. The backtracking is annoying, but it is in the game because we initially planned to have multiple exits from one room, and you could unlock dirrerent ones when you got different skills and so on. Without all that, its just a hassle.
As for the boss, he definitely isn't 100% polished. I personally managed to beat him after a couple of hours or so (so it should at least be possible). The whole point of boss combat is a bit different than in other games. He is trying to kill you using his abilities, but just like the player he needs stamina for that. So each ability costs him stamina. You basically need to survive that and you can use your own abilities to help you. The explosion just speeds up the fight a bit. Although running from the boss seems easy in theory, its actually really hard to pull off.
In general, there is still a bunch of polishing left to do, this is just a rough sketch that we had the time to implement.