No guide or walkthrough unfortunately. I was originally planning on one once but never had the time to finish it.

As to the forcefield, this only opens up when the final boss is beaten and is just another way to prompt the end of the game.

Okay, right.
Though I wonder how you would ever access it, because after the final battle you just walk out of the area and the game ends anyway. :D

How much time did you put into this mod, man, it's so long. Must have taken ages to build it.
Do you have any leveldesign experience? Because from what I can tell (I am a game developer myself) this is some A class level design.

The ONLY thing that is subpar are riddles without any hints. In game design, that's usually a big NO NO. Because there is no challenge associated with it, but only exhausting trial and error till you found the right solution.
That's really the only sin the mod has made in terms of game design principles.
The rest feels like you have some experience and this isn't the first time you designed a map.