I'm not claiming anything.
He shot Oswald at point blank range. Effective result.
None of the studies you bring up are specific to point blank range gunshots.
If the heart and brain are avoided, theres a good chance of survival. Which is why assassins actually shoot people in the heart or the brain!
William McKinley was shot in the abdomen from point blank range and it took him a week to die of gangrene.
James Garfield was shot twice in the back from point blank range and it took him nearly 3 months to die from it.
So, Oswald, the most important assassination in history, apart from the one 48 hours previously, and they're chancing a handgun shot to the gut to silence Oswald?
Does that actually make sense to anyone?