a good exercise i found for helping your finger reach would be to fret the lower E string at the 12th fret with your first finger play it , then fret the 14th fret on the same string with your middle finger and play it, start moving up the strings fretting and playing the same frets until you reach the high E string, then come back down the playing the same notes, once you get back to where you started at the 12th fret low E string repeat the whole process but move down a fret each time (11,10,9,8 etc..) until you get to a point where you can feel a good stretch in your fingers while your playing but can still play it without it hurting (if it is hurting then you have gone to far), stop there and repeat the process with your other fingers eg: middle & ring, ring & pinky.
you could take it further and play the whole exercise with your first & ring finger/middle & pinky but use a 2 fret gap instead of 1,
as for deadening strings, practice will help sort that problem but you could also try lowering your thumb placement on the back of the neck and see if that helps at all,
hope this info helps 
