Any one of the lengths/bows you mentioned would be possible.
The way to deal with the knot is to measure its width and add that width to the width of the limb at that point. Let your line follow the grain around the knot. Think of it like a stone in a stream...the water (grain) flows around the rock (knot)
Nature made it that way with no weakness as the knot is already compensated for as long as you follow the 'swell' of the grain around it and not cut straight lines through it. Add the width equally both sides of the limbs width if the knot is central (best) or if off to one side add extra width that side appriately. Remember to leave everything a little 'oversize' while roughing out and refine the area as tillering progresses.
The difference in ring thickness is no big deal, just check and double check thickness of the limb edges as tillering progresses. It just won't have 'normal' tapering ring patterns on the belly.