Okay I finally read through all of it and I compressed my general nitpicky-ness into two broad flaws in the overall writing. But before I got into that…the pros:
Excellent narrative overall, the story was pretty easily to follow and developed well as a steady progression. The characters were great and the mechanics overall which demonstrates that you are capable of writing better than those that heedlessly spams adverbs EVERYWHERE. Likewise the tension and set up was great and I did get into the story which is a major plus. However, there are two things that slightly irked me about your writing.
1.Major hand holding: this is a hard flaw to ameliorate at the get go since you have an unconscious want for your readers to follow along the narrative easier and understand what you are trying to convey in your mind (this in itself is a good thing). However, this is a sign of lack of confidence in the writer's part because the writer feels that the reader might not get the author's intention behind the story. This is apparent in the following ways.
-Obvious symbolism: After going through the story, I can see why you wanted to emphasize the comparison with the lights with the sun and the whole first sentence treating the cave in itself as en entity. However, the symbols are WAY too obvious and repeated too frequently to the point that it is almost insulting the reader. In my opinion, symbols should be a bit more subtle in presentation (yes you can still have the lights be representative of the sun which is fine, but don't wave the descriptions in front of our face multiple times to make sure we get it). Also symbolism shouldn't rely on suspicious awkward descriptors that are not normally affiliated with that object (i.e. Light coming into being). Symbols are something that the reader should come to the conclusion of after reflecting on the theme and the overall process of the story. In fact, it is more fun when the reader comes to their own conclusion on what symbolism you are aiming for. That leads to more discussion and debate on what the author is trying to communicate. However, if you make it too obvious, there is nothing to really discuss.
-"Telling" too much about the characters: Authors generally want us to know a lot about the characters and the story behind them which is why it is tempting to spill their history and their feelings and so on. However, this takes away some of the fun of interpreting characters and their motivations. Obviously you don't want to be TOO cryptic and go Camus on us, but you want to give the readers some space to make interpretations of the characters. Instead of YOU telling us how the character is like, how about having the CHARACTER tell us what he is like. That leaves it open to opportunities for the reader to question, "Oh is this guy credible? He seems to be losing his grip on reality...is this real or not? Etc..." which is excellent for the genre you are aiming for (Horror Psych thriller). A lot of details behind the character need to be cut out (mostly what YOU tell us during the present time and some during the flashback). Don't tell us what he's thinking, SHOW us what he's thinking and his physical responses towards it (heck you can do that in italics by writing internal dialogue which would be great as well). Don't forget that you're writing a horror psych thriller on the mystery behind our protagonist. Be a little cryptic and give us room to interpret him
2. Word Choice/Awkwardness/Utilizing Symbolism: I'm glad you are thinking at a higher level and trying to incorporate elements that connect together such as through symbols, flash backs, character history/development, and setting. This is not an easy task so I commend you for it. Unfortunately symbols are remarkably difficult to write in a coherent matter that wouldn't either feel 1.detracting 2.obvious and/or 3.unintentionally arrogant/condescending/preachy. Most amateur writers will have a hard time doing this because it DOES add a level of sophistication in the work but it sacrifices fluidity due to lack of practice. By trying to create symbols, you use particular words for the readers to make the connection that there might be something special about these "things" (lights, sounds, etc...). Unfortunately this makes the sentences awkward and they disrupt the flow of the story by having the readers pause, reread the sentence, go "huh?", and reread it again, and then spend a fair 10-15 seconds thinking about why the author went with that phrasing/word/etc... This also lends to strange, possibly misused descriptions or exaggerations.
Ugh, I think I rambled on for too long. Don't let this discourage you since you are on the right direction for writing well. These are VERY difficult to fix and can only be recognized through practice so keep writing (heck, I STILL make these mistakes myself since they happen unconsciously). You got the foundation well for writing a solid narrative so keep on at it. (Also LaCasina made a good point about the commas. Some of your sentences are too long and repetitive. I know you want to repeat some of them for emphasis, but it is unnecessary. Just let them go!)
PS: THESE sentences really bothered me:
- "He stared at the walls, trying to make out his aged face." Why did he want to suddenly look at his own wrinkled face in the middle of this expedition? Is it a compulsion thing? Seems really odd. (I know the reason why you added this as a descriptor, but the action in itself seems bizarre for this situation).
-"The cries of his daughter rained on him". I can see how metaphorically this works, but that would assume that she is crying ABOVE him and the cries are falling down upon him. So what direction is the cries coming from?
- "Alex counted to three admist the ever-louder tears of his daughter." I was not under the impression that tears made sounds. Unless she's "tearing" something, but that's a completely different word. Kinda confusing.
It is good that you are trying some creative words to describe things, but at the same times it could lend to a lot of misinterpretations like this (as well as some having unintended connotations).