Not sure how much help I'll be but I did find that once I had another kid in the house to consider, DD#2 spent more time napping in the Baby Bjorn and sling than she did in her own bed. Her sleep schedule was never the same from one day to the next for probably the first two years, but we hadda do what we hadda do, KWIM?

Looking at your schedule, you may want to try tanking him up before bedtime while changing that last nap to a catnap. In other words, something more like:
S 4pm-4:45 or 5PM
E 5PM
Short A time, maybe enough for a bath
E7PM bed.
That way his last 3 feeds would be 2 hours apart, so you'd be stuffing him full of calories toward the end of the day.
Just one thought.
