I notice that about 90% of pictures showing actual results of props shedding and hitting a fuselage show that the blades hit within a fraction of a degree of the prop plane. (Image-google "propeller blade separation").
And there is a good explanation for that - whatever the aerodynamic forces acting on the blade after separation, they likely have on the close order of 0.01 seconds to produce any relative motion fore or aft. Once released, the blade will be moving laterally at about 94m/s (339kph), and only has to travel about 1m to reach the fuselage (assuming it will hit it at all) on most transport turboprops.
(Math is: 2-meter blade, 1-meter half radius. At 1800 rpm the half-radius is travelling at pi x R x 1800 = 5654m/minute or 94m/sec average speed. The motion of a thrown blade is a pirouette around the blade's center of mass, tip over root, like a thrown boomerang).
Interestingly, in cases where the entire prop departs (gearbox failure and such) the prop almost always moves backwards - drag on a now-unpowered prop vastly outweighing any residual thrust. E.G. Marine C-130 crash, Mississippi, 2017 - #3 prop knocked loose by shock of #2 blade failure, went backwards over the top of the fuselage like the iceberg ripping the Titanic - dit-dit-dit.
As to "prop-proofing" the fuselage: at 94m/s, a prop blade will be travelling at only ~1/8th the velocity of an average firearm muzzle velocity (800m/s) - but it will mass about 333 times as much as the average bullet and have around 40 times the momentum (p, where p=mv). Kevlar won't do much - would require steel armor. Assumes bullet masses 30g and prop blade masses 10kg.