The Part time Captains are on salary (as are all pilots) and are paid 1/2 of what a full time Captain makes in salary. A 1st year full time Captain makes $60,000 (without OT) so a part-time Captain will make $30,000. However if a PSM based part-timer works overtime for 4 of his 20 off he will make what a full-timer makes, if the full timer works no OT. The only day rates are for OT and both a full-time Captain and a part-time Captain both make $700 per day in OT.
As for benefits a part-time does not get medical or vacation, only the full-timers get that.