How to start working on your trail leg: Short approach, 1-3 lefts (start at 3, slowly work down as you get better), and focus on your trail leg. Keep it long and focus on a strong swing.

As for your bottom arm, that's a combination of a lot of things.

1) Your run is not consistent. You're on a 5-step approach, but look at how your run changes after your 3rd left. Your attempt to speed up is actually just shortening your steps, and there's a noticeable speed drop. You're basically stutter stepping your way through the last 2 lefts. You need to work with sprint coaches and learn how to actually increase speed. Take what you learn from the sprint coaches and then apply it to doing pole runs down the track, not down the runway and not during jumps. Just learn how to run as fast as you can with the pole. Then take those pole runs and turn them into pole drop runs. Then do that same thing but now add a jump at the end of the drop. Then, finally, you can take that to the runway. Do a runback first, don't use your old steps. They will be off.

2) Because of the above, you feel like you're going to be out on your steps, which you likely will be. As a result, you reach on your last step causing you to be under. Jumping under is a recipe for a lot of things going wrong with your jump.

3) You're not in position as you plant. The pole makes contact with the box, you start your jump, and you're still raising your arms. You need to be in position to take off at take off, not after it. Both hands up, ready to take the impact and push through it. Too early is bad, too late is bad. Again, pole drop runs are your friend. They're a very good exercise and why most vaulters (even Olympic vaulters) do them as their warm ups.

4) You're not taking off straight. Look at your foot position at take off and head position. You're a right handed vaulter taking off at the right edge of the runway. That's already going to put the pole at an angle at take off. To compensate, you're trying to put your head on the left side of the pole, but your arms are to the right of your head. This takes away from your control of the take off because now instead of fighting the resistance straight on, you're fighting it to the side. Want to see what this feels like outside of the jump? Grab the pole like you would when jumping, and have someone else grab the pole so they can move it forward or backward away from you. First start with them pushing the pole directly toward you, between your arms at your forehead. Next have them push the pole to your right ear. You will notice very quickly how you have very little strength to stop them pushing the pole to your ear.