If I'm not mistaken, it looks like you're bending the pole before you leave the ground. Are you doing that? Are you trying to do that? Do you recognize that as a flaw? I can't tell for certain, because I don't have slo-mo on your vid. Your answers to these questions might lead to more questions, or some advice.
The reason I ask is that I can't see your body posture on takeoff, but directly after takeoff (when I was able to freeze-frame), you look like you took off under, and you look like you might have been leaning back on takeoff - or got picked off the ground instead of purposely jumping up and into the takeoff.
i.e. You need to strive for a free takeoff.
I'm not sure what you mean by your bottom arm screwing stuff up, assuming that you're referring to during the plant (pre-takeoff). What you need to do is reach as tall as you can with your top hand, and your bottom hand will just go where it needs to go to plant properly. As long as the top arm is fully stretched, that should be all you need to worry about during your plant. Other than finishing your plant with a strong jumping action on takeoff. i.e. Stretch your plant up even further as you jump.
And yes, now that you mentioned it and I looked for it, you're NOT stretching your top arm up as high as it could and should be prior to takeoff.
I'm not sure what you mean when you refer to "being tall" and "bury my head" in the same sentence. When I was referring to not dropping your shoulders and head, I meant as you're swinging/extending - not during the plant.
So any specific drills that I suggest will depend on what you meant - which part of your vault, and what do YOU think you're doing wrong? i.e. What do YOU mean by "bury my head"?
Please recognize that anything that you SEEM to be doing wrong during the swing/extension (like "sitting") is not fixable on its own. Any flaw there can ALWAYS be traced back to something you're doing wrong in your plant, takeoff, C, or whip/swing. ALWAYS!
Kirk