Same here, made a living doing it, why we tend to go complex.
20's F will not be kind to the system you are proposing.
Nipples will freeze in those temps, they need some heat, and with all those pipes it'll need a recirc loop. The horizontal nipples are best for heated waterers as the valve is...
I thought about something similar....decided it was way too complicated(too many factors of failure)....went with a 3gal jug and horizontal nipples that can be heated in winter.
I carry out a gallon or less daily for up to 20 birds.
You have 4 chickens?
Why the need for 5 gals...and insulation...