Well try with the left foot elevated, just like a classic guitarist. Keep your shoulders up and show us your chest! I really don't like that loose position you have in the picture!! And last, try to relax your right arm by lay it down on the guitar top.
You mean holding the guitar between my legs? That's fine, that works... That's how I do most my practicing. The problem with that position is that it gets harder to hold the pick correctly.
What do you mean by loose position?
Edit: The strange thing tho, is that when I sit by the computer and type and such, the right shoulder is slightly elevated, but that doesn't hurt, unless I'm aware of it.