I've played the game on top difficulty and gotten through the first 4 acts only being caught by the mandatory enemies near the end of Act 2 in the mazelike area.
1. If you learn the enemy routes and wear the right equipment to move faster, and you don't even need the gun. You just run away and they never catch up (with exceptions that you're meant to just not get seen by to begin with).
2. The game provides a ReadMe note when you download it, telling you the controls.
3. You have to explore the area and put together details for yourself, for example in Act 1, there are three pillars and on the big door, there are 3 animal statues in a specific order. By this point, you will have seen one of the statues, which should be a pretty big hint.
4. The struggle function does work. You hold and let the struggle bar build up, and release to struggle with that amount. If the circle appears at the bottom of you screen, that's a delay. Wait for it to end and hold again. If you're on top difficulty, that's when the struggle doesn't work.
I think the only argument I can agree with here is that when you do get caught after a chase in a crouded area, you'll often get tagteamed. And to be fair, the lack of instruction could apply to certain things in Act 2 with the lab doors being fairly hidden after the Wolf Boss area, but other than that, the game is designed surpringly well after, of course with flaws mind you.
With the game's full release now, it's possible that a guide will pop up on the Steam page in the Guides section that will offer a walkthrough for parts if you get stuck, so maybe give it a few weeks and come back if you want to.