Hmm let me see with those movies. I've never seen Population 436, but I've seen the rest. I basically reccommend all of them, but I'll add a few non spoiler thoughts.
The Lighthouse - Great movie. One of the best of 2019. Maybe more borderline horror, but there's more dread, mood, and atmosphere here than most horror movies.
Night Of The Demons - I don't see how you won't at least enjoy this, leather. It's punk as fuck and it rules. It's one of my quintessential Halloween movies.
Hereditary - Probably my favorite horror film of the 2010's. I don't want to say much else, but I will say that it's a horror movie I wouldn't really want to watch around Halloween time. The movie is depressing as hell and not really a spooky fun Halloween movie (It's probably perfect in the cold and desolate months of January and February), but as a movie it's incredible. Toni Collette gives one of my favorite performances in a horror movie in a long time.
Cabin In The Woods - I don't love this as much as most people, but it's pretty fun and is a really good movie to watch around this time of the year.
Color Out Of Space - Even if you hate Cage, you might be able to get something out of it. The visuals are stunning, the characters I think are pretty interesting or likable, and when the movie goes for it, it really goes for it. It's so great seeing Richard Stanley direct again and he still has quite the eye for some crazy imagery. The second half of the movie is wild. Cage does go full on Cage in the second half though and he would definitely be really annoying to someone that doesn't like him.
Mandy - Very similar to COOS in the visual style, but still adds it's own thing. I like this more than COOS as a movie. I think Cage is pretty great in it and the first hour or so is the most low key and reserved he's been in decades. His change to a more typical screaming Cage character felt natural and earned. This movie is fucking bonkers though and there's so many memorable scenes and characters. The guy that plays Jeremiah Sands outdoes Cage in insanity.
Summer of 84 - Took two viewings for me to really like it. I'm beyond tired of the IT/Stranger Things I LUV STEPHEN KING, DA GOONIES, AND DA 80's AND KIDS THAT SWEAR AND ARE HORNY stuff and the first half of this is all of that. Then the second half it gets very serious and overall I think it's worth watching. Rich Somner from Mad Men gives a terrific performance and really carries things.
Don't Look Now - Similar to Hereditary in that this is an absolute great film and one of the best films on this list, but I wouldn't watch it around Halloween time. It's a powerhouse most definitely though.