I have a fenced in backyard. I've had two hawk attacks. So yes, don't trust a fence alone! My run is 6ft tall, no top and under a HUGE tree, no hawk attacks there. The two times they got attacked was when they ventured into the yard without the shelter of a tree. No worries though, both girls survived and healed back up. I just try to prevent folks from heartache.
And do yourself a favor: Do not skimp out of wire. Get hardware cloth or something similarly sturdy. Don't buy chicken wire. A raccoon or dog will tear through that like it's nothing.
I start my babies on flockraiser/grower feed, day one. I don't do starter, just not really needed. Just more bags you have to finish before starting the next. Layer starts around week 18-20 (depending if I am running out by week 18, or closer to 20. No sooner than 18 weeks though). Some folks use grower feed all the time, simply providing oyster shell on the side. I can only get that stuff in crumble = waste. Pellets last me twice as long as crumble
Can't really tell you how much you'll need, as it really depends how messy your 'kids' will be. Starter/grower is more waste than food, sadly. They just looove to dig in that stuff, poop in it and do other 'non-eating' activities with it.