This looks nice but Why didn't you just drill a hole throw the back of the housing in a slight downward angle (downward from inside, upward from outside) and that would remove one more pulley?

Or better leave it as it is but ADD some counter weights through the pulley above door. Just enough weight so the door is heavier. Much like the way garage doors work but they use springs. It would have taken the stress off the motor to almost nothing. You can make the door nice and heavy so predators can't lift it. There was a video of how a guy made a door (unrelated to chicken doors) where if the door was trying to be lifted the counter weight won't help, it was only when the motor pulled from the motor side that the counterweights engaged. It was so simple it only used a loop knot , an eye bolt and some common piece of hardware to make it work. I just can't remember how he did it. If I find the video I will come back and link it if you replay with interest.

Of course there is the option of putting the counterweight with spool on the same axle of the motor that has the primary Spool. when the motor turns on and starts pulling the door up it also let's down the counterweight which takes the stress off the motor. But is the motor is not running the total weight of the door is holding the door down. I don't like it as much as the first method because the first method would keep the door closed but will also keep the door from coming crashing down if you used cheap string.