This looks OK to you? Possible outside wall (not sure but I see plywood)? No metal plates protecting them? I run pipes, electric and even low voltage in the middle of bays whenever possible and protect them with strike plates whenever needed.
Just curious, how do you run a ten foot pipe in the middle of a two by four?
I agree there should be metal plates protecting the pipe; however how do you know he did not put them in. He may not have, but it is impossible to tell from the picture.
No, as stated earlier it is a sloppy job so it does not "look all right" but IMHO there is no reason to believe it will fail.
Yes, the mixing valve should be supported.
"Clarity to Agreement" Dennis Prager