Pulling a 68" bow, any bow, to 34 inch's is really pushing it, especially with Hickory. I know "some" stave's will get you there "but". I am not surprised at the "H" fracture. If it were my bow I would CA it, and back it with raw hide (go to trade forum and ask). My alternative would be bamboo backing, which would raise the poundage and fix the back, and it would look good stained. Use Urac 185 glue for boo/hickory bond. At 68 inch's and 55# or so the speed should be in the high 140's fps.
Dick