(Grrrr, ran out of edit time)

First, you really don't need powered or fan assisted intakes. Your exhaust fans will create enough vacuum to pull fresh air from the passive intakes.

You WILL need a carbon scrubber, or some kind of odor control. I haven't found a strain yet that is not stinky in flower.

You should lose the mylar, go with flat white paint. Almost as good reflectively and much easier to install and maintain.

If you make sure your plants get enough fresh air, you will have no need for CO2. Get all your other things (lighting, ventilation, nutrients, etc.) dialed in perfectly before even thinking about adding CO2.

Pay serious attention to your ventilation, I cannot stress this enough! When growing in an enclosed area, you have to have a way to get fresh cool air into the box and a way to get stale, stinky, hot air out. All without letting in extra light that you don't want.

A hint on ventilation: draw it out on paper first. To use your exhaust fan(s) efficiently, the fan should be the last thing in the ventilation stream. The fan should always be pulling through the carbon filter.

I believe I gave you the link to the grow room setup sticky. That helped me immensely.

Good luck.