There are these cd's that help with relaxation, stimulation etc, the brand is "brainsync" they can stimulate different brainwaves, anyways they have "sleep" ones for delta brainwaves. The sounds are soothing and relaxing just like lullaby music ,etc. If you play one he might actually fall asleep and stay asleep. Just an idea though.
I cut down the naps my little 9, almost 10 month old, to 2 naps during the day. Her bedtime is at 8 so her last nap is usually at 2. I let her sleep for an hour. Then I wear her out playing, and crawling around. I give her a warm bath at 7:30. Nurse or Daddy feeds her. She is out. It took a week to break her habit. But she's gotten use to it. Good luck :)