Looks like your shoulder and hip pitch changes in the downswing to very flat. Not sure if maybe feeling like your right hip and right shoulder going down at the ground more, or your left hip and left shoulder going up more will help keep the club from rerouting so much.
I started out with the overlap (Vardon) grip. Over the years I have experimented in practice rounds with the double overlap and even the triple overlap! I've also played with the concept of the trigger finger down the grip. All "mad scientist" experiments. All failures... but I learned something. I learned to never do those things again.
It's one reason I swing normally at about 85%. My carry distances are all at 85% swing. That way if I need that little extra it's there. I can go to 95%. I don't ever want to go to 100% - this is where bad things happen.
I don't know if you can learn by watching Ernie Els swing 1000 times on youtube.... but it's worth a shot.
Depends on the golfer. Some might feel like getting the arms down sooner will help. Others might feel the hips. It's what ever feel works to produce a consistent swing.
If you want specific advice, post a video of your swing (create a My Swing thread).
11th hole on Southern Pines on Saturday. Short dogleg right. Only 270 yards but I'm not a big hitter so I decided not to try to carry the bunker up the right side and play it straight up the fairway. I ended up pushing it right a bit but made excellent contact and really got into it. As it was flying towards the trap I worried it would come up short but somehow it managed to carry it and roll out to about 20 yards from the green. I left myself a 5 footer for birdie but missed the putt. It was by far the best drive I've hit in a while even if it was technically a miss.