It seems like you need to spend a lot of your training time on the vault and the throws. You can't be a good decathlete without these events, and they take time and technique practice, not just raw ability!
There really aren't any shortcuts, except to not form bad habits which take forever to fix. Watch this video and pay attention to what David Butler is saying...little details of the pole carry and plant really matter!http://youtu.be/3YkbsmYlR28
Also here are some key drills for you:
Measured pole runs: on the football field or track, use tape or yard markers to develop consistency in your run and plant. You can't improve until you develop consistency!
Keep working those plant drills while walking, jogging...you must teach your hands to work in timing with the feet to get your hands up at the right time. This takes 1000's of reps...no shortcuts here!
Run up a few steps, jump and catch a rope as high as possible, then swing upside down. This is one of the most useful all-around drills for learning the complete motion of vaulting.
Another one that might help you: run/jump up to a highbar and try to keep your hips from swinging forward (you must catch the bar at the right spot, keep the knee high, and the trail leg back). This helps teach you how to reach the proper position at the takeoff for moving the pole/staying behind it, and setting up the swing.
Also, grab a bigger pole. The one you are using is too small. Take a bigger one out to the football field and do the "jump-over-the-tip" drill (jog, plant high with top hand, keep pole centered, hang and ride the pole over). Also jump into the pit on a big, stiff pole from 3 lefts, trying to stay behind the pole and move your grip up as high a possible. Don't swing. This will improve your takeoff and help you learn to jump from farther out. Your goal should be 5-6 feet above your standing grip.
Good luck, welcome to a fun event!