There's way too much going on there for the first page. When you fully flesh it out, you may find that this sequence of events is your entire first chapter or very nearly.
Right now, it's a wall of text. It needs some white space. Split it into readable paragraphs (ex: The start of the dream sequence should be a new paragraph). Also, take a look at other horror and thriller novels. Some of them use line breaks and white space to slow the action and create suspense.
IMO your protagonist is thinking too rationally and precisely for a dream (ex: "approximately three meters," "lack of light sources"). Someone dreaming might realize it's dark, but they probably won't look for potential sources of light. They tend to operate more on emotion and instinct than concrete, rational thought.
You have some good ideas. Keep chipping away at it.
A prof of mine once said that writing is like making a sculpture. You don't sculpt the perfect foot, then the perfect ankle. Instead, you carve the rough shape, then you start refining it until it slowly starts to look like a person, then you work on the details.