Hey DaddyMac
If a coon can reach a latch 37 inches off of the ground with nothing to stand on, I'd seriously suspect a bear did it and not a coon! There is not a scrimshin of difference between the difficulty factor of a barrel latch and a carabiner.
Your coop appears to be cock-strong. However, this thread couldn't be a better example to prove how ridiculous some folk's replies can be. Really!!! Using a pig to climb.
Don't be discouraged. The vast majority of the folks here will bend over backwards to help you. As ridiculous as it may sound, I believe the folks with the goofy suggestions and ridiculous videos, were originally trying to help. But, if you don't drink their Koolaid, they go postal on you.
Used gear oil might have small metal particles in it. But, metal shavings have practically no possible poisonous or toxic effect on us or birds. Unless, of course, if the particles were large enough to cause intestinal damage. This is not the same thing as the heavy metal toxicity present in human sewage.
Everything that makes used motor oil toxic is the deposits from burned and unburned fuel. You have not used it on the interior of your coop so, it is a moot point anyway.
When coons become able to pull off 2X6s screwed with 3 1/2 torx screws, I'm moving, Even if it means moving to the arctic! Just about every coop you'll find in the "coop building" area of this site has ventilation covered with hardware cloth. Why would this one in particular, be susceptible to being ripped off by a coon? Has anyone here ever heard of a coon ripping of hardware cloth that was fastened securely?
I thought leaving that poop crack was ingenious! No shoveling. No fuss no muss. Just hose it right out of the coop. I'm pulling the bottom board off my coop and doing the exact same thing.
Now I'm worried that the coons might pick my Master lock or figure the combination to my other locks. And, we already know that they can hover in mid-air to manipulate latches.