At first I was a bit surprised that you talk of dexterity issues while these exercises are within 4 frets. Then I looked at that picture of you with your guitar. If that is your standard left hand position then you're making some things more difficult than they are.
For anything that requires some stretches your thumb should be right behind the neck (of the guitar, not your neck :) ) and the palm should be parallel to the lower edge of the fretboard. You can get the right starting position by placing your stretched out fingers on the fretboard so that every finger lies parallel to his respective fret. This should work with no tension and no stretching at all. Remember the position of your thumb and your palm and keep it that way while you play your usual exercises.
I can get my mom's digicam tomorrow and make some pix to illustrate that if it helps you.
If you watch some female classical players you'll notice that even with small hands most chords and scales are a matter of proper hand position rather than flexibility, though these players have both of course.

Marcel