Confused about polarity of Transformer
2 is Wurth's number for centre tap. It's needed in push-pull configurations. Actually there are 2 primaries in push-pull systems and the center tap is only a drawing habit due their serial connection. The halves are used in turns. You need only single primary, no need to make the centre tap.

"The parallelled 3" should NOT be ignored. That can be 3 identical windings in parallel to make the losses smaller. 3 wires is better than a thicker single wire due the skin effect. Refer the documentation.

Wurth has thought of 2 secondaries. Low loss full wave rectifier needs them. You need single secondary, but again check, if it must be 3 identical windings in parallel.

Wind all windings to the same direction. The dot is the starting point of the winding. Fail in this => wrong pulse polarities => smoke.

Unused pins are harmful only because they need space.