Now I'm not sure what your trying to do. Of course if you have a mix of different note values then each one will require different treatment. You cannot globally apply a duration amount to different values. Each note needs it's correct start and end time to make any musical sense.
You'll just have to go in there and drag each note out to where you want it.
Ultimately if you want your music to sound right then you need to PLAY IT that way. You can only do so much to manipulate data and ya, it very time consuming to make a silk purse out of a sow.