Rabbits are a good source of meat, as is any other butchering that you might do. I doubt you will ever throw away any meat ever again. When to start RAW? Now is good. You also might want to get some Diatomaceous Earth as part of your daily feeding if you are going to feed straight from live. The DE will stave off any worms or parasites the bunny may contract. If you have a good sized flock you may want to do a monthly butcher just for the dogs. I am not sure if you can feed an LGD off his flock, that could present an issue. My BB don't have a high prey drive but the have some, and Jade is obsessed with gophers (her favorite food). I saw DH's post regarding prey drive in the Boerboel and I totally agree. You do not need that sort of drive in a farm protection dog. Just a willingness to guard and protect.
Oh and you will not need to wait for him to grow. Just feed him normal and if he wants more adjust his meals but watch for chunkiness. If he starts to get pudgy reduce his portion. It's better if he runs thin while he is growing. Pups that start thick and heavy tend to have joint issues and it's not even later on that the problems arise. He will grow so fast you can watch it happen.