The idea of using a cocobolo pen blank for tip overlays sounds good. But don't worry about tip overlays at this stage...that is a really unimportant feature which you can always add later to any bow.
You'll probably need to make at least one decent bow before you should attempt the bow you have in mind now. Learning how to work with wood, how to handle tools, how to make a lay-out and how to make the wood bend your way, are very important steps. Trying to make the bow pictured in your openings post as a first bow, is doomed for failure. As a first bow, take a single board (no laminating) and make a bow. You could steam/heat in some recurves, which is already making things more complex (but still manageable in my opinion) for a first bow.
Birch is not a great bowwood. It can and has been used (run a search), but is pretty weak in compression. Hickory (or osage, if you know where to get it) would be a better choice.