First off, if you want to make a temporary double out of your triple, just remove the inner chainring, or set up the derailler such that the little ring is locked out. Problem solved cheaply.

Second, the only reason downshifting would ever get to the point of being that hard is if you had your high stop screw set too far in. You are hitting the mechanical stop which is why it's so hard to get the shift to complete. By forcing the shift to complete, you are risking breaking your shifter. How did you go about setting up your front derailler?