The dragon is 350kg, and should be able to fly up to 2.5 km above sea level.

Gravity and atmospheric pressure are normal.

There isn't much of a limit for the muscle's strength and bone resistance, but let it at least be plausible, enough for the creature to be able to flap the proposed wing size and a bit more.

The flight is like that of a bat, able to fly up and down, as well as glide — which will be the main transportation method — up to speeds of 180 km/h.

the wing shape is that of a bat's and if you can add anything to improve efficiency, the better

It would be much appreciated if you showed how you figured out your answers.