As for exercise:
a) have you asked your PT people for suggestions? Upper body weight lifting, and eventually swimming will probably be good choices once you are cleared for them.
b)Have you checked out the Seated Cardio Videos here on Spark? I've done them several times, (as I was prepping for the aftermath of foot surgery). I did find on some of the moves that I had to be careful not to put pressure on my foot to help stabilize me, so you would need to watch that probably. Perhaps you could get the PT folks to take a look and see if they'd be appropriate in your situation!
Take it slow and easy....get it healed right the first time is the most important thing!! In the meantime, you can focus mostly on getting your diet in control, so you are just maintaining your weight rather than gaining. Best of Luck!!