Shaimano road shifters have four main positions plus a trim position for the smallest chainring. When downshifting from the big chainring to the middle it should take one click. The second click will put the derailleur on the second middle position. A third click will shift to the smallest chainring. I think you have too much tension and the low limit screw my also be set too close to the seat tube.
I suggest that you follow instructions for setting up a front derailleur found at http://www.parktool.com. Perform each step in proper sequence leaving nothing out. When set up correctly there should be very little tension on the cable.