Worse, if I feed in 95,0,0 convert to Quaternions, then convert to Eulers, I have 85,180,-180
This is correct!
Work out what angles the two Eulers give you in real life. They're identical.
The QuatToEuler functions given here just give you *one* correct Euler angle. There are many identical Euler angles that can be expressed in different numbers.
It's like a square-root function: what would you expect sqrt((-5) * (-5)) to return?