Is the game linear or is there a way to affect how things change?

Would/are there any?

Does anyone know how exactly the score is calculated for zombies? I'm playing on Nightmare difficulty and every time I kill a zombie for xp and possibly supplies, my score gets lowered. Is that for Nightmare, or is that just the way the game is programmed?...

how is the performance on integrated gpu? like from 10th gen intel

There doesn't seem to be a way to use the consumables that increase your max HP. Also there doesn't seem to be a way to exit the game without ctrl+alt+del. Also it seems weird that all Melee weapons cause damage to the character when they are used unless it's a one hit KO....