mmmh
You have a story, that s a nice plus. However, remember how most of these games start: With the player being absolutely alone. The player being able to communicate with HQ from the beginning kind of contradicts the dark atmosphere you are building up with your - nice (!) - graphics. I would recommend to start with the player writing into his diary instead at the beginning, and having him to assemble a radio from parts he finds in a labyrinth afterwards. From then onwards, I would sometimes let him write into the diary (when I want the atmosphere more gloomy) and then again let him communicate with HQ (to lighten up the atmosphere again) Best source for radio parts would be dead groups of other warriors.
Then, I would only add one player as a companion that you find, and have him killed by a surprise monster attack when moving onwards (They could pincer him from left and right side while he is on a platfrom above you, so the player would see him fighting desperately).
The gameplay suffers a bit from the tiny differences of surface height being mandatory to crouch and kill the enemies, and from the double jump height being incorrect in comparison to the height you can actually reach.
Respawn points could be marked in the landscape somehow.
You are almost there. Fix the jump height bugs and consider adding to the story at the beginning, and you will have a decent game.