Regarding the deep litter method - my understanding of it is that it is really a method meant for an area with a dirt floor so that composting goes on. Otherwise, it might not be so sanitary. So,if you have a cement floor, there wouldn't be anything beneficial, necessarily, to do the work of...
I have a roo that has feet that look just like that. They seem to be even more swollen on hotter days - so today they looked very swollen. I took him to the vet a couple of months ago but didn't get any help there. The vet thought maybe it was caused by trauma from jumping down off the roost...
Pulling for your drake! What a good boy trying to protect his duck. I just lost a drake a couple of weeks ago to a fisher (I am pretty sure) and his girl is missing him! She still has other ducks to socialize with, but you can tell she is still missing him. Will keep your boy in my prayers.
Your fully feathered duck babies should be fine if they are left out so long as they have a place to snuggle down into the dry bedding (it sounds like yours do). Are you certain though that their area is predator proof? That would be my biggest concern for them right now.
Ok, I read the first 20 or so posts to this thread and the last few... clearly you are all having way too much fun with this and I really have nothing magical or moat-ish to contribute to this, but I can still give the thread a bump in the direction of 1,000,000 posts.... Good luck!
I would try to block off the nesting boxes at night for a few nights and actually pick them up and put them up on their roost. Pretty soon they should get the idea. Just be sure you unblock the nest boxes first thing in the morning so they don't lay on the floor.