I actually enjoyed the story (the few parts that make sense and the ending).
The game lacks a few additional dialogues or something. Especially near the end and in the last level.
I don't think so. The odd dialogue near the end was rather fitting. The protagonist is hiding something even from the player! The problem is the extreme discord between the gameplay/what the player is experiencing and what the characters are experiencing. All the characters are very emotional and freaked out, but the player rarely encounter actual danger in the gameplay. The horror in the game is non-existant, but the characters behave like it is ever present.
The greatest discord between gameplay and story is in how 2/3 of the game take place outside of the controlled experimental environment. In the early part of the game the carefully planned puzzles make sense. Once everything starts falling apart and you leave the test areas it doesn't seem very likely that you would find puzzles set up wherever you are going. You could argue that cthulhu set this up through his agent but that is an extreme plot contrivance to motivate the gameplay.
The story, however interesting, is in the wrong game entirely!