Help with batch replacing background

I have a large number of pictures that were taken in front of a green screen. I need to do a few simple actions, but I'm having a terrible time getting the automate function to work. 

What I need is to:

• open the picture
• remove the background
• hit the auto button in camera raw filter (or some other method of quickly touching up the photos)
• drop in a different picture as the new background (plus a little repositioning)
• save the new picture.

I've largely gotten it working, but I'm running intot he problem that the camera raw filter seems to just be whatever settings the auto button spits out when I record the action. I did my best to keep things consistant when taking the pictures, but there's enough varience that a lot of them look pretty bad when they're all adjusted using the same settings. Is there a way to automatically, auto-adjust the filter on a picture by picture basis? 

I have a similar problem with positioning. The people in the pictures are not all positioned in the frame the same way. This is a probably a long shot, but is there a way to auto center them or otherwise crop the pictures without risking cutting off parts of the subject?