no, that leaf curl isn't normal. i'd check the plant problems area on the forums. maybe start a new thread and fill out the troubleshooting form. love the grow box! now as for the freezing temps, i'd pick up some reflective insulation. its like bubblewrap covered in a mylar-like film. you can see it in my pic of my lights. that with a small space heater should keep it good. yes passive intake is no fans in, all fans out. and yes the pvc pipe will need a sharper angle. keep it up, sorry for not posting for a while.