I think it's fine for kids younger than teenagers. Maybe around 8 and up. By the time they are teenagers, most kids are watching anything and everything, included R-rated movies.
I wonder how I would have turned out if more sheltered growing up. I think I was around 7 when i watched Childs play and Nightmare on Elm Street. Then here you are saying some flames killing a fake looking big rat might be too scary for kids.
I just heard an interesting fan theory, that the scene with Artax and the swamp represents being unable to help a friend or family member through depression. That for the friend it can be perplexing (move or you'll die!), but it's so hard to do anything for a depressed person in a slump.
My husband has a close friend who's currently going through a rough patch. We know our Artax will pull through, but it's going to be hard going for a while. Meanwhile my husband is trying to at least keep in touch.
It's all you can do sometimes. When the darkness sets in for me I can't recognize the light. I'm starting to break out of it somewhat, but there's a lot of self hate still etched in. It does kind of improve once you're on the other side.
I watched all that stuff as a kid too, I remember having nightmares for weeks over Children of the Corn. I want to avoid that with my kid and let her choose when to watch that stuff.
Oh, I chose to watch it all. It's just that my parents allowed it. Lol
Oddly enough, the only thing that I ever remember getting nightmares about was an alien abduction movie called "fire in the Sky" that said it was based on a true story. That one kept me up at night.