Welcome!
That's a lot of questions in one topic...
Cut an oak tree of 5 to 8 inches in diameter. Split to quarters. Remove bark. Seal the ends. Put to dry indoors for four months.
Go to a hardware store or lumberyard and buy an ash/oak/elm/maple board. In contrast to the freshly cut tree, this wood will be dry and ready to work with. It'll allow you to make a bow straight away.
In the meantime, spend every hour of spare time on READING! I think - but I could be mistaken here - that you've actually read very little. This message board is actually a very poor start for a beginner to start. It presents all kinds of stuff in an unorganized and overwhelming way. I would highly, HIGHLY advice you to buy the first volume of the book The Traditional Bowyers Bible. Also read all the internet build alongs you can find (
these, and
these to start with).
Buy a spool of Dacron B50 and learn how to twist a flemish string (google that term) from YouTube tutorials. Takes one day, saves you many dollars.
Unstrung bow length depends on many factors, draw length being the most important factor. For a stiff handled flatbow with your length, I'd advice you to start with 66" overall length.
Any specific questions? Please ask!