Two pins producing sine waves 180° out of phase will get pretty close to 7V RMS as the voltage difference between them varies from +5V to -5V......will need an RC filter to turn the PWM signal into an analog voltage,
Just product a square wave
Just produce a square wave and send through an integrator, you will have to calculate the values required and may need 2 stages.
No, integrator will make a triangle wave.
@MarkT: The DAC output is between 1/6 * 3.3V and 5/6 * 3.3V.