I have seen (trail-cam) a raccoon climbing up a bare post (8x8) of treated lumber to get from my work platform onto the duck-house's tin roof, so i am sure they can climb any kind of wooden or wood like surface. Back in Houston i have seen a family of raccoons climbing up the cement-siding of my neighbors house to get into the attic…
2" gap - that's about the same that i have in my duck house, not wide enough for a 'coon, idk about 'possums and skunks, but weasel & co fit easily through 1" and less. I have see a full grown Raccoon male squeezing itself through a 4" opening (pallet) to get to my duck food stash. Fortunately he could not get out after filling his belly and i found him stuck in the morning, bad day for him…
Larger predators like Fox, Coyote, Lynx, Cougar, … are easier to keep out with sturdy building material than the small ones (weasel, mink) or the clever ones like Raccoons.
Are you using a carabiner or something equally complex to lock the door? 'Coons are intelligent enough to open latches, for example. And i have heart stories of raccoons luring poultry to the fence with food, grab them and drag them through piece by piece.
I consider Raccoons to be the greatest threat to my ducks and electricity the only reliable defense measure. Once they have burned their greedy paws the don't come back.
		
		
	 
Since the fox attack we now lock them in the coop house itself at night, they are in the run during the day and free roam when we are home and have a constant eye on them. I've also been leaving the back door open for my dog to keep watch as well. When it comes to animals we are in Wisconsin in a very small town. We have neighbors all around but its population of 600 and all double lots with lots of woods. That being said weve had 2 fox hanging out in town the past couple years, raccoon and skunk. 
-Coyote shouldn't be able to fit through my hog panel back yard but if they do they are unable to get into the coop building. I've also never heard or saw any come within a mile of us. 
-Opossum I have only saw 1 in my entire life living here
-skunk I dont believe can climb and the bottom of the coop is secure, we do have poultry flooring on the coop floor raised 8" however since the fox i have been placing a sturdy box on one open end and a few board on the other to keep anything from reaching up in or tormenting them from under
-fox would be unable to jump, climb or fit through any of the 2" holes on the 8ft section of the roof but I do worry with the new addition if they would be able to scratch and chew the fence panels so I'm likely going to line the bottom 4ft with panel that way if they chew through one they would come to another that is solid and flat.
-raccoon I started double checking everything today going off of articles I have read and what you've said. My chores today and fixing the latches on both standard doors, somehow creating a lock for the sliding coop door incase they do get into the run itself where the coop door is and adding a few screws, bent tin and ordering wire mesh for the 2" gaps. I never even thought about them getting to the coop roof from our roof. It would be pretty easy climbing the hog panel, jumping to our roof and making the foot stretch from ours to the 2" opening in the back of the coop. 
I'm damn near embarrassed I missed so much information!!! I'm highly educated with small indoor animals, dogs, cats, and farm animals not to mention spent WEEKS researching duck info but you learn something new everyday! And it's sad to say I used to trap these animals, worked at a large scale pet store and a dairy farm but it still went over my head. I'm going to attach a few pictures if it will let me to give you a better look for understanding and possibly tips.