"Most" is a line of components from Pinarello, a very respected company that has never offered junky or substandard parts. Assuming this bar and stem are authentic (not counterfeit), it should be high quality.
That indeed appears to be a compact drop, which is a shape of bar that many people favor for modern road bikes. 44cm is kind of wide, but the size that will work well for you is very subjective and depends a lot on your body. (Wide shoulders/chest = 44ish is good. I have narrow shoulders and prefer a 40 or even 38cm) Some people feel a wider bar helps with breathing, by opening up the position of your torso a bit.
Most modern road bikes use a 1-1/8" steering column. In the era when your bike was made, not all did. It's best to measure before buying the stem, to be sure. If the asking price is good, you could gamble, and then if the stem does not fit your bike, you'll still have a nice bar and can get a stem elsewhere.
I would not sweat the weight of the handlebar. It's not made of solid iron. It will be fine on your bike.
There are no issues with using a 6 degree stem on a frame with 17 degree head tube. People mix and match these angles all the time. If you want the stem to sit parallel to the ground (some people care about this for purely aesthetic reasons), then you'd have to match them, but otherwise it's no problem. You can even flip the stem over to get positive or negative 6 degrees, depending on whether you want a more upright position for comfort or a lower position for better aerodynamics.