Adjusting a triple front derailleur after removing largest chainring
The chain line expected by a double front derailleur is basically what comes with the largest two chain rings on a triple.  Since you are using the smallest two chain rings, the double front derailleur will not shift optimally.

Instead, I'd suggest keeping the triple front derailleur in place.  Using the limit screw -- as you already have -- is the best option.  Given that you are unable to use the trim shift, at the moment, I believe that you may want to back off the limit screw just a bit.  In doing so, you'll allow the front derailleur to move outward a little more, which should allow the trim to work properly.