The basic triac switcher won't work with a PWM signal. The zero cross detector in the MOC3041 won't allow firing at arbitrary phase angles. An MOC3011 would be needed along with a separate zero cross detector and voltage controlled timer connected to the firing circuit.
Also, I believe the 56 ohm resistor is burning up because the load is too close to the latching current of the SCR. The SCR can't latch itself on until the voltage is above 50V or so. In the meantime, the 56 ohm resistor and optocoupler are doing all of the conducting. The 330 ohm resistor doesn't fry because it's in parallel with the gate-MT1 resistance which is generally quite low.
How about this DC Controlled Light Dimmer Electronic Kit K8064?
http://www.apogeekits.com/light_dimmer.htm