The Transplant Part is my wild guess
Remember The mc evolution to stage 2 ?
the one voice told mc not bend knee for the 1st
that voice use symbol The eye
sooo maybe mc's eye indeed special one
My wild guess ?
Mc mom killed by the someone got infected from either the 3rd or 4th ( the one MC didn't Choose )
then MC dad killed the infected
and knowing MC lost his eye decided took the infected eye and transplated to mc
or for better twist and more tragic
MC mom got infected from either 3rd or 4th
but failed become berserk like kenny and hurt MC too
MC dad want stop infected Mom and kill her
he took the eye and transplated to MC
afterall MC father always dodgy about truth Mc mom death
I wonder What MC father job is ?
Maybe Monster hunter ?
he not have superpower
but have power of prep like michael before got infected
it will badass is that true
And about the black monster in the dead end
Maybe that thing Is the big bad the one mommy and daddy want to kill
But That thing too strong Crushing mommy like bug
that why She need army and secret weapon to kill black monster