The intake coming through the top port in the 4x4 is coming from the AC vent in the celling. I have an AC Infinity air tap fan in the AC vent to boost the flow. I also have a port at the bottom with a 8’ length of 6" ducting in a 90 degree bend with a fan blowing air from the room in. Everything is exhausted through the top with a carbon filter and 6" inline fan out a vent I put in a piece of PVC sheet good placed in a window opening.
I had some serious heat issues, it was getting 99 degrees in the tent. I had to figure something out, It’s still getting up to 88 degrees now. My son is moving out this fall and I’m going to claim his room for a grow space, I plan to use a portable AC unit to coo the room instead of the ghetto set up I’m using now.
Dealing with heat has been a PITA for me at times too.
The important thing is root and leaf temps.
I’ve found that leaf temps are about 8 to 10 F lower than the ambient tent temps so long as they are well watered.
Root temps are important too, but larger pots help.
It looks like you have it well under control, nice setup!