Thanks for the input.
I think I may have found something that is working!
Instead of staying in his room until he is asleep, I leave while he is still up. Most of the time he's actually standing in his crib, but not crying. I leave the room and he starts a whining/cry. He then fall asleep within 10 minutes, usually 5. Since I started doing this before his bedtime and naptime, he has been sleeping for an 8-9 hours. He'll usually wake one or two times during the night, but puts himself back to sleep within a few minutes. I was really hesitant to leave the room while he was still awake, but other than a bit of whining, he's putting himself to sleep. I think because he is a "spirited" baby, I was too much stimulation. This has been working for several days now, so something is right.