For a grow space that size I would only use 1 x 5" fan and it would be an exhaust, you can have a passive intake (just an intake, no fan needed) as it will save on noise and electricity. I'm not a soil grower (I do hydro) but would definately say 1L pots are way too small, certainly if you want to veg to 10-12" as they will at least double in size during flower. Probably at least 3 or 5L pots would be my guess, maybe bigger, but no doubt an experienced soil grower will have a better idea than me.

As for yield, that will depend on every factor of your grow. Depends on strain of plant, type and wattage of lighting, temperature, nutrients, pot size (!), etc etc.

I would hope to yield about a pound from a growspace of your size (7.5 sq. foot), because I get in excess of 6+ ounces from 3.5 sq. foot with my hydro setup and the strain I am growing. This current grow, I hope to get 10+ ounces from the same space by growing 2 plants instead of 1 and a 400w HPS instead of a 250 HPS, hope it pays off.

For the size of your space I would think about a 400w HPS instead of a 250w for flower. More light = more buds....

Hope that helped a bit...:hippy: