Using both PWM and Timer2 interrupt in PIC18F25k50
I can see no reason why not. It's quite common to want to synchronize with the PWM, and the interrupt from the timer is most commonly used.
That's a little more tricky. You can use the Timer 2 interrupt to trigger a sample, but you want to do a block sample starting at the interrupt time, really, don't you?  Unfortunately it doesn't look like that chip has DMA, so it would really be a case of using T2 to start the sampling, but drive the sampling from another timer / interrupt.