[Silent Hill 1] Confusion on some Symbolism [SPOILERS]

So I finished Silent Hill recently and have been going back watching theory videos to help fill in the blanks of stuff I missed. Most of it makes sense and lines up with clues in the game.

However one thing that confuses me is the symbolism for some of the enemies. It seems commonly accepted that the Groaners come from Alessa's fear of dogs, and Air Screamers come from her reading the Lost World (or a similar title, i can't quite remember) and there being a creature similar to it.

My question is, is either of these aspects something hinted at within the game itself? Does the game ever imply Alessa being afraid of dogs or reading that book? Does the servered dog head mean something about it perhaps? If anything the Air Screamers being based around a fear of birds would make more sense to me, since the bird cage in the hospital could represent a bird in ward near Alessa whose noises scared her, or something.

Similar question for the meaning of enemies growing worms out of them since people seem to just assume she has a fear of worms. Also less important but it seems odd to me people assume Lisa seeing insects getting into the ward was a result of her hallucinations from the drugs, when if they were real it would explain the heavy insect symbolism as something that also scared Alessa.

Sorry if it's all a bit of a jumble of thoughts but just curious if there's something I'm missing here. It's really cool to go back and connect all the little pieces.