I wouldn't be discouraged at all with a oak board that has 1.5 inch of set. That's pretty darn good in my book.
You can buy compression, lifeless boards, all day long at Lowe's or any other place that sells boards that are straight, flat, pristine to normal board buying standards off the self. Now finding one with acceptable grain is a little more challenging but can be done if you take the time to sort through enough stock.
What you don't see is all the tension strong material that was discarded or not selected to start with because it was reflexed, deflex ed or just plain warped. Nobody wants to buy a board for flooring or building anything else in this condition.
In addition to that, the grain has been violated, regardless that is inherently weaker as a result.
Wood with attitude is what you are after, the sawmill is a great place to shop for boards. Building a bow from material without seeing it standing is always a gamble but close examination can help prior to selection.
All bows have set, you can't expect to bend a piece of wood almost twice its length without giving up something. The belly fibers compress as a result; you will never get that back, just part of the process. Don't bend your bow backwards; your right, that's a no-no. It will only weaken it further.
Bows that you see posted with flat profiles or holding reflex, have either been heat induced or naturally reflexed from the high tension properties of the wood. Woods with attitude.
An Oak board bow with an 1.5 inch of set is pretty darn good in my book.