I'm really sorry to hear your story- A loss of a beloved no matter what it is will always be hard. To have your new ducks trust you try to constantly feed them, have them associate you with safety/food so you'll have some happy ducks in no time!
Do make sure you check on her every maybe 2 hours or less? Or you can just do it every day once if you sense that she's doing good.
Your main opponent to this situation is a possible infection or more maggots growing on her leg knub, make sure you do apply some sort of medication.
I completely...
First, To get the hen you should try suiting up, just in case he wants to pick a bone with you. I find trash can lids as shields work best. But you can also use a broom! (just don't whack him, of course.)
If you're intimidated by your rooster there's really not much you can do other than...
Ah, 3 Roosters to 7 Hens is horrible.. Overmating probably happened.
Another issue I can think of, and I had this myself is that the roosters aren't letting each other mate with the hens. My roosters used to attack each other-- and still do but they calmed down. That was until one tries to mate...