Head movement is fine. The modern golf swing has a lot of that since it encourages a squat type of move to generate power. Check our Rory: https://www.youtube.com/watch?v=e1BHA8hGd-c Try to track the Nike logo on his hat and you'll see how much he moves around.

The main issue with the pull up is it describes early extension. That is when you thrust your hips forward and lose spine angle through impact. This is what proper spine angle at impact looks like: http://jeffygolf.com/attachment.php?attachmentid=319&d=1330749154

Early extension looks like this at impact: http://www.adamyounggolf.com/wp-content/uploads/2016/02/early-extending.jpg - notice where the butt is in relation to address and that the spine is almost vertical instead of maintaining the tilted angle similar to the address position.

There's a laundry list of causes on this but it's one of the power zapping moves in golf swing. The causes can be physical like not being flexible enough or mechanical like taking the club away or being stuck on the downswing so you have to extend to create room for your arms.

I would go see an instructor and get their opinion on this. The bottom line is early extension can be causes by a ton of things and if you're not sure how to fix it yourself (which I take it you're not since you're posting here), it's going to be really hard to fix it using the web without causing other issues. It helps a lot to have an instructor move your body into the right positions.