Caloric Intake for Healing Broken Bones

In general, eating at maintenance is a good idea when you're ill. Set MFP to maintenance and eat that amount.

To the best of my knowledge, no one can say exactly how many calories it takes to heal multiple fractures, but I would not want to be in a deficit at all if I had those injuries.

I would also not worry too much about mild or moderate weight gain while healing. Some of what you're seeing is probably water due to inflammation; we don't know how much, if any of it, is fat. You have some pretty serious injuries and the priority should be healing, not weight loss.

As @apullum suggested your weight gain is probably all water retention related to inflammation. That number may go up and down while you are healing. I would not expect to see your pre-injury weight for quite some time.

Your energy expenditure is higher while your body heals itself. You should also plan to err on the side of gaining a little. The faster you heal the faster you can get back to whatever your health goals were before this accident.

Take good care of yourself. Follow the doctor's orders/restrictions and mend fast.