Hey the best advice I could give you is do what you fell is the most comfortable. When I first started learning people tried to tell me how my body should be positioned when I played and it never worked. You gotta find your own way to play. After all everyone plays diffrent.
And as for your chord habits, their actually easy to break if you keep practicing and practicing its just like learning a new song because when you learn a new song sometimes you make the mistake of going to a diffrent fret or using a diffrent chord because thats what you were used to from another song.

So just keep practicing and the problem will fix itself!