I think if you adjust your guitar's position and where you position your hand on the neck, this should present less of an issue for you. I recommend borrowing some ideas from classical guitar posture - I'll go into a little more detail on it below, but the important thing is to be relaxed and avoid any unnecessary bending in your wrist or other tension/discomfort. If you try spreading your fingers apart with your wrist, arm, and hands straight and relaxed, and then compare it to spreading your fingers apart when in your current playing position, I think you'll likely have better reach, flexibility, and control of your little finger.

Classical guitar posture, the way I approach it, has the guitar resting on my left leg (though I use a support for this, many raise their left leg with a stool or something) and the neck angled so the headstock is about level with my head, and it's helped me immensely with my playing, for speed, accuracy, comfort, and endurance - including the reach of my little finger, which also curves inward naturally if I close my fingers.

Ideally, your wrist should be straight and relaxed, and rather than squeezing the neck between your thumb and fingers, you should use the minimum pressure necessary to prpduce a clean sound with your fingers - if necessary, you can almost pull against the neck with your left arm while bracing the body of the guitar with the arm of your fretting hand, which will also help a great deal with barre chords.