Tips on upgrading my secret garden

I have a secret garden with a secret door. Its hidden so well that hordes of people could come over and never know it there.
Its 11.5x10x4.5 feet. I have two 600 watt lps lights hung with parabolic reflectors.
The room is vented with an 8inch inline exhaust fan that comes on once an hour for 15 minutes all day, which is filtered through to a charcoal filter. The intake is my garage that takes in cold air from outside. It is very cold at this time of year and every time the exhaust fan turns on it pulls in very frigid air.
Im growing 47 plants in 6 inch pots with sunshine mix #4. I tried to grow scrog but vegged to long.
I am having a very hard time keeping the temp and humidity right. Since the air that is coming in from the garage is cold and dry.
I have attached pics so you can have a better understanding of my room. If anyone has any ideas on how to improve my secret garden to improve the climate controls, I would love to hear them. I am very new at growing indoors and do not understand how to keep the temp regulated when pulling dry cold air in. It is definitely slowing the growing down.

What are the trouble temps and humidity? It really comes down to money. You can get a climate controller and hook it tona humidifier and dehumidifier. This should take care of that. You can set your exhaust up to a thermo so it only turns on when it's needed. If you don't need the cooling then just have it timed to run long enough to evacuate the and change out at the whole room once an hour.

Could seal up the whole room and plumb in co2. Still need the climate controller and then maybe an ac unit.

Make the floors white, black is just wasting light.

Get some oscelating fans to circulate the air.

I agree with karr that a little more info the temps and humid would be helpful. I suspect that running a kids vaporizer that you may already have on the cycle timer that runs the fans will help with the low humidity.

Really I have been told that light under the leaves is bad and it will burn them. As for the temp during the day time when the lights are on the temp is 72 but drops to 61 when the fan comes back on. It takes about 40 minutes for the temp to rise again to 72. When the lights are off it about 61 for 12 hours. I know this is to low and need to fix that. As for the humidity I have no Idea. i have no more money to spend to buy a humidity sensor to find out. Is there any way to bring the humidity up. I do know that the air is dry and needs a boost.
What about the reflectors. I have been told that parabolic reflectors is good for vegging and really nothing else. Is this true? Do the parallel reflectors reflect light more directly for flowering or do they both give the same results?