Our flights are generally 30 hours when there's a dog involved. They do not let them out, and unless you have some higher-level tests done, you can't collect your dog in Seoul and spend some time with him or her overnight.
Our dog has never defecated in his crate, but he does generally urinate. It's not bad, and he generally spends a few minutes finishing the job when we let him out at the destination.
We have a smaller dog so were never close to the weight limit, so I can't really comment there. I would just remove the water bottle prior to weighing if it's close.