I would start with a fan on window #5 which would throw out the (hot) air at a faster speed.
Normally the pressure will try to normalize and this means that colder air would flow in from the other rooms.
It make sense. Outtacke fans should automatically create an ariflow. Until now I tried adding intake fans in 2 and 3 positions and instead of lowering temperatures I got an awesome +10°C in the room Normally the pressure will try to normalize and this means that colder air would flow in from the other rooms.
What do you suggest for the 12x24cm hole I have on the side of the wall (4) considering that there's fresh air in the other room?