In my view The questions about blade behavior are way too technical for this kind of thread. The same questions and faulted assumptions keep popping up on multiple posts.
The blades, behavior once it has separated is governed by Newtoian physics and not by aerodynamic forces which are pittance compared to the Newton laws of motion. So put the blade air loads out of your mind.
For the blade breakup into multiple large pieces, it's extremely plastic at these impact strain rates and column buckling is taking place. The forward motion is due to sliding friction of the blade tip once it strikes the case.