All the info and reviews on the USMC Ka-bar knife that I've read (my search history is fun as are the ads that get suggested to me) pretty much align with this one:
A full history and in-depth review of the KABAR USMC fighting/utility knife. This is the most legendary knife of this century and is still made in the USA.
www.wellrigged.com
re: the tip
"The clip point itself is not sharp but it is beveled for easier penetration in tactical situations.
A clip point has its advantages and disadvantages:
--Very efficient penetration ability
--Excellent slicer"
the efficiency of the blade:
"I butcher plenty of chickens every year. Without getting into the gorry details, I’ll just say this knife is the most efficient “slicer” I own. A single pass from the KA-BAR’s 7-inch blade does very clean work of a dirty job."
I've already posted YT videos I found where people use it to cut through multiple water filled gallon jugs in one sweep. And there are plenty of YT videos where people demonstrate using it to stab and/or slice with slabs of meat/hunks of pig carcass (not going to go back to find those links because I really don't want that populating my feeds again).
BK had a sharpener, so you know he made sure his was as sharp as could be. Even an uncoordinated swing/slash with an extremely sharp 7" blade is going cause severe damage. He wasn't a 90 lb weakling with no upper body strength. And poor fine motor skills isn't the same as having poor grip strength.
What indication do we have that Ethan was standing because I've seen just as many indications that he never got out of the bed? And on the off chance that Ethan had gotten up, all indications were that he would have been waking from sleep as well as having been drinking a lot the evening before. BK would be fully awake, not drunk or dealing with the after effects of alcohol, and would have the element of surprise+adrenalin on his side.