At those temps You can probably skip the heat; yes, do go for a heated dog bowl type waterer; I had to laugh about the Christmas lights...because we do that!!!
Good tip about the wider roosts so they can keep toes covered. If you don't want to change your roosts you can just screw another board...
No heat is safest...
If they can huddle up on roosts, that helps greatly. Deep straw/pine combo bedding gives our girls the option to get down off the perch and huddle there instead if they prefer.
That said, our first year we had only a few chickens and thought they needed supplementing...we...