Running through the finer details of Pinan Nidan kata with my students.
The first move is not about using the fist like a hammer to hit something directly to "block" it. It's about using the whole length from elbow to fist to drop down and cover the width of the body. Likewise, for movement 4, the principle remains the same, but the angle of the arm is different because the width of the body facing the opponent is different.
As you move forward for the second move to make junzuki, just hold the right shoulder back a bit.
On the turn after the second kiai point, ensure you turn your body around enough so your belt not is facing 45 degrees. I would say check that your back foot is at least pointing to the front otherwise it will impede a fuller turn. If you don't turn enough, then you end up doing a sideways shuto strike if you are not careful rather than a straight on nukite. The turn I made, I kept my left hand by the side of the body and imagined pulling that further back to train the core movement. It's OK to have a more central position with both hands back to back, but do not pull them towards your body. Have your elbows slightly in front of your ribs. Make the imaginary line from your solar plexus, through both hands to your target. Also, the stance "neko ashi" has width between the feet. All those centres line up.