I will guess that the light is different. That's why you broke everything. And some days, everybody breaks everything.
I would pressure flake a beveled edge on that blade and make a neck knife. It is a good shape and length for a necker. As you use it and resharpen it, you will work past the hinge, when you do, you can try to run a series of pressure flakes down the blade to thin it some but I would not, it will be be getting narrow and the thickness will strengthen the blade. Once you actually start using stone tools, you won't be quite as impressed with the super thin show pieces. There are certain things that really thin is great for like arrow points, but the thicker ones also were made deliberately. And most knives were thicker than the replicas most modern knappers make, they had to be, your life might depend on it not breaking.
One last thing, you did not fail. You made a knife blade. It may not look like what you had planned but it had a few quirks that you didn't know about when you started knapping it. You actually over came and solved some problems that you didn't know that you could. It actually made you a better knapper.