If it were mine---and it's not----I'd get panda film. I would screw a 2x2 from the back-left corner to the front-right corner at ceiling height, and staple the panda film to that. That will give you an even split. I agree that ya don't need that much space to veg, but unless you move the door, a cross-corner split seems like the best alternative to me.

As far as ventilation...just look at other set-ups to see how they've done it, mix in your own ideas, and pow--you got ventilation.