Tip thickness depends greatly on what style of string nock you're doing and how fine you're willing to go. Thinner is better, up until the point that they break. On my current 45# bow, the nocks are just a hair thicker than 3/8" (that's fairly conservative for the bow type) and you could certainly go a lot thinner on a kids weight bow. Then again, I could easily see a kid tripping or being careless or whatever and breaking too thin of a tip, so it might be best to overbuild them some anyways.
Re fade taper: So, you have the static handle which doesn't bend, and the working limb that makes up most of the rest of the length of the bow and does bend right? The fade is the transition area between the working limb and handle. The taper here would be meaning a smooth transition or a harsh transition. I'm with knoll on leaving the handle until after tillering. It's easier to get it to sit level on the tillering tree when it's flat. You'll see all about that soon. Also saves at least some work if the bow breaks in tillering.
Also, to be clear, when I asked about taper earlier, I wasn't meaning across the width of the bow, but rather had you thinned down the belly side of the bow when those pictures where taken?
I would really like to see a good picture of the grain on the back of the bow. Depending on how good the grain is, brown paper can work. Linen and drywall tape are similar options. If the grain's too poor, something sturdier would be in order. Rawhide maybe, or even changing up for a working backing in the form of a good piece of hickory or something. It just depends.