The club swings on an incline angle, it does not swing "down" towards the ball. When you transfer force to counteract the swinging club, be sure you are pushing away and not "up."
Creating width is not a matter of how far you can move the clubhead from your body, it is how far you can distance the club handle from your chest. Creating width is the first step to increasing distance with your driver.
What happens to the driver after impact? If you intend on increasing speed, your arms will allow the club to re-hinge. If you prevent this, you increase tension, which slows down your swing.
Step 1: Create Width. Step 2: Push away - transfering force away from the direction of the swing - not up. Step 3: Re-hinge the club; this requires relaxation, which increases speed.