Well 4x4 is plenty of room. It just needs good ventilation. You can rig something ghetto up or buy something fancy, either way you have to have good ventilation. exhausting from above is going to reduce temps big time. you can continue to feed it that stuff for the first couple weeks of flower, then you need something with less N. For now just get it into a bigger container, a dark one, and under the HPS 12/12.