I like the idea of this overall story as to why this man wants to go back in time to forget things he learned or go back before things got hard or unmanageable, I feel like there's a lot more to be explored with that concept. I also think the stealth aspect of the abstract time corridor is a lot of fun, there's definitely some neat ideas to be explored there.
The controls feel very awkward. If I have my right hand on the arrow keys and my left hand on space, I need to take my hand off the movement controls to rotate the camera, and if I have my left hand on the arrow keys and my right hand on the mouse, again, I need to take my hand off the movement controls to press space when I need to interact with an object. I feel like a better way to use the arrow keys like that would be to take what older resident evils do and use tank controls, but then again, that kind of control scheme doesn't really fit well with a stealth type game. Probably just sticking to WASD to move and moving the mouse for the camera might be best. Also having the camera that close to the character doesn't really give a whole lot of room to view your surroundings, so having a more zoomed out camera might be better as well.
Giving this sad depressed man the ability to go back in time to relive happier memories is a really neat idea that could be implemented well. Maybe later on in the story, he learns that he can't change the past no matter how hard he tries and that he needs to learn to live with the outcome of whatever happened could make for a neat story. As you go through these memories you find out more about his past and what lead him to the life he's living today can be something very compelling, and I would love to see more!