My baby is the same age and just recently organized/consolidated her naps during the day so now on a good day it's pretty predictable. a morning, afternoon nap (both long-ish) and then a short nap around dinner time.
I think your DS's bedtime is pretty late? DD goes to bed at 7 and then sleeps until 7 (not straight through or even close. waking to nurse every few hours but it's definitely her nighttime. no extended waking).