Just design it to break into the right number of bits!
Fluid Flow
"probability of heading in the direction of the wing of 165/360x3= 1 in 0.7 or 1.4:1 "
I think if you get a probability > 1 then you should start to worry about the calculation a little. Assuming your 165/360 is fair then you need to be looking at:
1 - (195/360)^^3 = 0.84 as the probability of hitting the wing. (Think of the opposite of all three missing)
Your other figure is hardly affected.
Of course, I assume the number of bits is also a variable here, interesting and nice to see that if it breaks into enough bits the formula for the chance of a hit becomes a certainty but there again the "bit" in question would have little mass. If someone lets us know at what mass these bits are nolonger a danger to the wing then "all" you have to do is design in a weakness for controlled (but more frequent) failure and you have "Containment". Unfortunately there are also an infinite number of these things so at the end of the day it probably just comes back to an energy calculation unless you can get it to fall apart slowly, spreading the energy release.
Apologies in advance - not an engineer.