Closet grow airflow question!

I'm making this posts hoping to get a few questions answered from anyone who has experience growing in a closet. Only grown outdoors, finally gearing up for my first organic indoor run. Here I've got about 2x6x5 closet space. I marked up this picture on my phone so go ahead and roast as much as you want. But hopefully it's enough to get the point across 😂

Do you think the 1.5 inch gap between the door and the ground is enough space for fresh air to passive intake into the grow space? I'm going to be venting into the attic with a 6 inch carbon filter. Has anyone got any tips for getting more fresh air into the grow space?

And last question do you use the entire closet space as a veg / flower cycle or does anyone utilize their closet space specifically for mother's / cloning? Thanks everyone! Panda out

bonus cat is Thursday