One thing you should IMHO check is your knee bend. A bent knee promotes a good slide and keeps your body's CG "under" your body, which also helps with balance and a straight approach towards the foul line.
Another thing I suggest (from personal experience - I also use a 5 step approach) is to keep your initial steps small. I used to hurry much too much during the initial 3 steps, which totally killed timing with the pendulum. I was much too early at the foul line, had to wait for the ball, and had almost no slide at all. I got much better when I learned to start really slowly, with just half an initail "trigger step", and just gradually speeding my steps up once the ball was on its way. I also start from the last row of dots, but actually only make a larger "power step" (when the ball comes forward again, adding the pendulum momentum to the footwork forward) and have a relatively long slide. Far from perfect, though, but it helped me a lot with timing, leverage and overall balance and control.