Deep Litter, Ducks, Predators, and Ventilation

[Kangasox]

We have an 8x8 coop and 10x10 run that we are getting down to the nitty gritty with finishing For ducks We plan to coop them at night, the coop is a shed we built, but we are not craftsmen, so there are small cracks (can not slide a shim through). There are also the cracks at the top with the galvanized roof ridges. No cracks are very large, but it's not airtight. We are also putting in 4 4"x8" vents, and there are 4 windows and a louvered door as the coop door. All are additionally protected with hw cloth.

Is my ventilation good?
I was planning on sealing up all cracks, but then read for deep litter, ventilation is key.

Are there any predators who can slip through thin cracks and will do harm, either to the ducks or as vermin?

Thanks!