1 inch wide is quite narrow for the oak wood, so it would be under more stress with non working handle.
Let handle bend, just like other bow you make, this design is perfect for it and spread stress evenly over bigger area.
I think longer is better, but it also depend draw length.
When tiller, you want make so bow is barely bend in handle at brace. (If put against wall, a 12" section should only deflect 1 mm or so)
Set in the middle of bow is biggest speed killer, more set caused more deflection at the tips than if the set were near the tips. You need to get your outer limbs bending before the handle to get this right, since the handle doesnt need to bend much, you can fine tune it during last stage of tillering.