Leave extra width round the knots... you can always remove it later!
Knots on the belly (if sound) are not a problem. Knots on the back have no strength what so ever, and if you look at it as a missing 1/4" of sapwood then the extra width replaces that (and follows the flow of the fibres) without making it too stiff.
The mistake I often see is people leaving a bulge on the back where there is a knot AND a bulge on the belly, this just creates a rigid area which may not appear to be a problem, but it creates a weak point either side. Often you'll see two knots treated like that with a thin point between them which is asking to become a hinge.
Try to get smooth even continuous sapwood on the back.
Like a lot of things in bow making, you can make compromises. I've laid out bows on the diagonal with a stave like that, but as Mike points out, that gives problems of one edge being lower that the other which is tricky to tiller. If it's just slightly out it's not too much of a problem, you can use heat to correct the twist, but then you can use heat to correct the sideways bowing!
It's all about compromise and making the least bad choice! You can't always tell which way is best, and both ways may well make a fine bow.
Often the solution is a little of A and a little of B.
I've found that correcting twist is relatively easy, whereas a big bend at the grip is harder to do...
This is why you need the pencil... keep drawing lines until you think you've got the best compromise.
Del
PS in your last pic, there is a dip either side of that knot, just let the side of the bow swell out gently round that as you may need to allow for that dip. Like I said when in doubt leave extra, it can be taken off later, but it's harder to put it back on.
