yea .. agree ... also seems to me that reading would be your best choise right now .. do a lot of research .. and you might be able to pull a pound after a few trys ..
after all it is you who is surpose to grow it ... I cant do it from here .. I like to help .. but get the basic in place fist please ..
google it .. see a few pics and vidios of it .. read a few guides ..
this is a nice one for a new grower with a lot of questions:
http://www.420magazine.com/forums/how-grow-marijuana/81264-how-grow-marijuana-everything-you-need-know.html
I would think the good space you got and the good penetrations of a 1K HPS would inspire to grow a bit taller/bigger plants ..
but I guess its a question of tast .. want to use 30 seeds and haverst in 10 weeks or use 8 seeds and haverst in 14 weeks ..
but tell me what kind of medium are you growing in ? and what kind of nutriens do you have ?
and did you make sure you have a big enough ventilation to keep that 1K light cool and a carbon filter to remove the stink ?