It's not defined as such in your Eagle file, I think. But I leave that up to you to figure out.
Probably, but I think you can get away with a far smaller one. This one goes up to 300W, but you only need a fraction of this. I think if you get one that goes up to 5A you're already good.
Again: assuming the NEMA's etc run on 12V and only one HX711 and the Pico need 5V.