It seems that the only point that is not covered here is the making more money part, though I am sure that you have put in plenty of time thinking about it. Are you sure that you could go back to the old salary if that is what is offered to you since it was also a major stressor that caused you to seek out different employment?
Would you also be able to go back to the long 4 days and do the other clinic job again? I am not just talking about would they allow you but it was stressing you a great deal working so early and late every day, especially in winter, even though you did like having the late days on Mondays.
Are you sure that you could be far enough away from your old supervisor that she could not poison any enjoyment you get from your job there, even if she was not your supervisor? Getting the info secondhand she seemed like a vindictive and manipulating person that would thrive on sowing discord to ruin your job and/or reputation no matter where you were, but I have not been in the hospital nor met her so I am not sure that it would be possible if you were no longer under her. I certainly hope not.
Going back is just the easy answer to fulfilling your passion. There are other avenues and knowing you I don't think you will stop until you are doing what you were meant to do. Good luck and I hope that you find your happy spot soon.