I hope gloopo sees this, because I speedran your game. I found three techniques, and one skip so far, and will be improving my runs.
1. Ghost crouching, crouch during the crouch animation and you get the speed of standing with the hitbox of crouching.
2. Ramp boosting, running up a ramp/stair and jumping causes way more height.
3. Strafing, just walk diagonally to go faster.
The skip is valve skip, which is self explanatory, and you ghost crouch and ramp boost in the stairs at the water section and completely skip the need for the valve. I hope more people run this game soon,
Here is my run: