too much variation in Temp-HELP

Man I'm having severe temperature change in my room (4x4x drops to 65 during the night then up to 90+ during the day.
I'm running an inline vortex fan but sucking the air out dose'nt work so I'm blowing air in from out side. the light is a 1000hsp. I think I've stunted the little guy or girl too early to know yet.Starting to pull my hair out over this an believe me I can't lose anymore hair ..lol

thats suppose to be 4x4x8

is your light air-cooled? if not, that is what i recommend and use two fans - one for exhaust and one just for air-cooling that 1000 watter.

you might consider using those high temps to your advantage and invest in CO2 injection - but that will be much more pricey than an air-cooled hood and another fan.