I believe your numbers are wrong.
Lets say HP and Attack are 31 IV, this leaves 4 other stats. If you want Defense at 32 you have a 1/32 chance. But I say I don't care which IV is perfect. There are 4 stats left to be rolled (Defense, Special Attack, Special Defense and Speed), as each of them has a chance to roll the perfect IV it has to be a lot higher than 1/32 to get at least 3 perfect IVs.
If you want at least ONE head out of 4 coin flips. The odds are much higher than 1/2 as well.
I guess your calculations are wrong, still haven't figured it out yet and my knowledge of probability in school has vanished :(
I guess this is correct to have at least 3 IVs in Friend Safari: 1 - (1 - 1/32)^4 = 12%, which matches my own experiences of catching about 100 Dittos so far. Still not sure what the propability of 4, 5 and 6 perfect IVs are.
On a note: I am catching Dittos, can't breed them, sorry. :(