Michael was wearing a bulletproof vest throughout the movie
- That's how he survived the six shots to his chest!
- A vest that he got off of a Smith's Grove Sanitarium guard that he killed during his escape.
Michael chose to go after Laurie and her friends after Annie yelled at him.
Yes, he's stalking Laurie at the old Myers house, but how's he supposed to know who sits where in the classroom? For all he knew, Laurie could be sitting on the opposite side and not notice him. The first time he actually reacts to someone onscreen is when Annie yells "Hey jerk! Speed kills!", doing a Brake Angrily. Then he subsequently follows Annie and Laurie around town. Plus, Michael goes after Annie first, watching her arriving at the Wallace house, sneaking into her car and waiting there until she gets in, then slitting her throat. If he really wanted to kill Laurie, he'd go for her first. The reason Michael didn't kill Tommy Doyle was because Tommy believed in him.
With Improbable Infant Survival averted in Halloween 2018 that leaves another reason why Michael did not take the opportunity to kill Tommy Doyle when he had a chance to do so. Throughout the day Tommy was trying to warn everyone that the Boogeyman exists, but nobody believed him because he was just a scaredy kid. Michael may have decided he made for a useful harbinger and set himself on killing some of the others for ignoring the warning. Judith didn't have sex at the start of the film.
A lot of people have noticed how short of time for Judith and her boyfriend being upstairs in the opening scene from the time the light went off that Michael witnessed from outside to the moment the boyfriend begins to leave. Now, many people may think it was a quickie, or that the boyfriend may have pumped and run, but there is a third option that is just as likely, if not more-so likely: Judith and her boyfriend didn't have sex. There's a good chance that they got to second base, and Judith allowed her boyfriend a good view of her breasts while making out, but she may have stopped him from going farther and the boyfriend respected her enough to honor her request to wait, and when Michael killed her, she died a virgin.