the first photo looks like there is a wave or bump in the grain where the wood is starting to splinter. If the back of the bow is perfectly flat and not following the bump in the grain then the fibres will have been violated.
De-crowned wood must follow a single growth ring and all the lumps and bumps in the grain, if fibres are violated then splintering will occur.
check the whole length of hickory backing to see if grain undulations have been followed faithfully.
You could back the bow with cotton, linen, rawhide or sinew, if a single growth ring hasn't been followed then I would back the entire length of the bow.
Beware a
longbow with any other backing than wood isn't a
longbow as far as GNAS are concerned!
But a broken longbow is just kindling to light a fire with!
As far as tillering goes, the bow looks too flat in the handle and too whip tillered at the tips - if you want to check each limb is tillered the same amount, then check this by floor tillering. If one limb is stiffer you'll feel it against the floor.
Good Luck