I had another go tonight and the majority of the issues seemed to be performance based, I can't tell the actual framerate but it seemed pretty low and the game tended to hang at the beginning and end. I also had a one off issue with the cursor not locking when restarting the game meaning I couldn't look or shoot, I had a similar issue with another Godot game yesterday. I was able to get better control of the jetpack this time even with the low frame rate but it was a challenge and you definitely couldn't aim and shoot at the same time.
I'm a bit puzzled about what could be causing the performance issues as you don't appear to have any highly detailed models or textures, and the world doesn't seem that big, which would make me look at the game logic, maybe your AI is doing something too often or when it doesn't need to.
With regards to the controls it felt like the WASD keys were axis aligned, so W moves you north, S is south, and D and A are east and west accordingly. Typically in a third person game the A and D keys rotate the player and W and S move you forward or backwards based on the characters current heading.
That all said I think you've got something pretty good to build on and I hope you continue working on it after the voting finishes.