Hey there... I'm a rabbit owner so here's my advice...
1st of all, take a deep breath. Your dog doesn't understand what's going on & quite possibly just wanted to play with the little bunn so don't be upset with him. Give him a little snuggle.
I am pretty sure there's a good possibility that he Momma is going to disown the baby now (but we cant be sure!). Again, it's not yours or your dogs fault! I would definately recommend calling your local animal shelter & asking for advice.
You would be able to possibly care for the baby until it was old enough to be placed into a new home, but I think it would be a very difficult task especially with a dog (& to be honest I'm not sure if he'd make it because of the young age PLUS he's most likely still nursing at this point so wouldn't be able to eat solid food.. also I hate to mention it but rabbits have very fragile backs so he could have been hurt too badly by being flipped over)
I completely understand how upset you are right now, but I definately think your best bet is to get someone from an vet's office or animal shelter, etc to take care of things.
That's about all I can think of. Hope I was a bit of help!