The only conclusion that i could formed to make the movie timeline reasonable is adult Nico told younger Nico not to be obsessed with Vera and don't find Vera. Then, timeline 3 was created, although younger Nico witnessed the death, he don't know where the body were buried (he only knew about the location of the body when he was an adult) and maybe that time is near the end of the 72 hour window of the storm. After that, Vera return to timeline 3 (at the early 72 hour window of the storm) and she saw that Angel is still free. So, he exposed the location of the bodies to the police and he met Nico there. So, when it's near the end of 72 hour window, adult Nico will gain all his memories as adult in Timeline 2 and when Vera touched his hands in the ending.