What breed are your ducks? Pekins can tolerate -20F.. Other breeds not so much. I would definitely, at the very least, insulate your shelter and provide a LOT of straw.
Name - Elizabeth
Age - 4.5 Months
Breed - Silver Appleyard
Gender - Female
What makes her special - Since Elizabeth was 3 days old, I knew she was the alpha of the flock. She has a very distinctive loud quack to round up the rest of the group.
Name - Henry
Age - 4.5 Months
Breed - Silver Appleyard
Gender - Drake
What makes him special -Henry is a gentle giant. I've never had a duck that has such a sweet disposition.
Even though your Pekin may be too large for a hawk to carry away, a hawk can still do a lot of damage. Other predators to be concerned about: fox, raccoon, bobcat, weasel, owl. Let him free range during the day and put him inside the run at night.
I have a ramp on the outside of our pool and a set of pet steps on the inside. The steps take up less room. They don't need all of the steps, just the top two.
Clipping wings, I cannot help you with as I have never done it.
I use a 20 quart heated bucket that I got at Tractor Supply. It cost about $36.00. I've used it for 4 years now, works great. I will be purchasing another one since my flock has increased.
I used this for my 3 Pekins. It worked well until they went outside full time.
https://www.tractorsupply.com/tsc/product/tuff-stuff-products-heavy-duty-oval-stock-tank-110-gal?cm_vc=-10005