Wrong output for phase demodulation
You tell the phase demodulator that the signal has a maximum phase deviation of $\pi/2$, but then you actually use a signal with a phase deviation of $5\pi/2$ (due to the amplitude of the message signal). This doesn't make sense.

Note that even the most ideal phase demodulator cannot distinguish between $\cos(2\pi f_ct+\phi(t))$ and $\cos(2\pi f_ct + \phi(t)+2k\pi)$, $k\in\mathbb{Z}$.