Finally reached halfway point (I think) on my story. Now things should get hectic with the arrival of Taylor, Hannah and their friends as the mystery behind the bear suits, the cave and the figure in the darkness start to unfold.
On another note, I changed a little my idea of alternate endings. I was going to write a story where the end could be branched into Zack choosing one of the girls, but now I thought about another approach. I think it would be best to drop the alternate endings on different points in the story where each one would fit better. For example, if you read page 70 of my story, you'll see that Zack is prompted to make a decision, to refuse Lisa's advance or take her back as his girlfriend. In the "canon" path, he'll refuse her and the story will continue, but if he chooses to take her back, it'll trigger the alternate path to one of the endings, the one in which Zack stays with Lisa.
And finally, regarding the sequel, I'll definitely write the short story about the weekend the characters will spend at the cabin on the summer following their high school graduation. I'll do it like I said before, on the beginning of the story I'll leave it open to the writers to choose with whom Zack finished the first story and go from there.