Heyyy Ill try to simplify for ya!
You have a fan that sucks air from outside your tent, and blows it in...imagine now your tent is a balloon and its blowing up...if you poke a hole in it air will come out of the hole because theres high pressure inside the room.Any air leaks will be blowing stinky air from in the room, to outside.
Its being suggested you remove the fan from this part, and just have a hole to the outside room (light proofed of course). Now when yo take the air from inside the tent, and pump it outside the tent, you can imagine all the walls folding in if there was no air leaks....now if you poke a hole in it the inside of the tent is at vacuum, so any holes will mean clean air from outside the tent rushes in...no stinky air will go out of the hole as long as air is rushing in.
The trick then is to have the right sized hole for air to come in...you want enough air to not pull the tent down, but not so much theres no pressure...your walls should gently suck in a bit, not too much!
+rep if i helped please.
prot