you will often find that your 3/4 swing is indeed a 95% swing. If you look in a mirror or window reflection, your 3/4 swing is likely reaching parallel. your 100% swing is probably over the top, and your hands cannot recover in time and are behind you, leaving the club face open.. your hips have blocked your arms.
If you must swing at this 100%, try to start the downswing motion with your hands (just a millisecond before moving your hips). This should help you get your hands through better.
Finally, my best drill, is to put a tee in the ground about 12 inches behind the ball. The tee is ligned up with the middle of the ball.. if I'm hitting well sometimes the tee is 8" behind and lined up with the inside edge of the ball. Your take away and swing should not hit the tee.
If it is, your swing plane is too upright and you are not hitting from the inside. This is crucial to hitting a draw.
Lastly, try your best not to sway your head 1 inch. A real twisting of the body should help, and swing from in to out.