How do I get my subjects sharper?

When you are shooting wide open like that, make certain you are aware of your own back to front motion. This won't show up as blur, it won't get compensated for with stabilization, and you will hardly notice it while looking through the viewfinder. But if you focus and then lean towards or away even a small amount this will change the point of focus and at wider apertures you don't have a lot of room to play with.