Have you tried teaching him to fall asleep on his own? What I mean is putting him down to sleep before he's actually asleep? We lie down with our 2-year-old for a few minutes of "cuddle time" then put him in his crib awake. He talks to himself and eventually goes to sleep...usually within 5 minutes of putting him down.
I know you have a newborn, so this might be a difficult thing to try right now, but perhaps you and your son could have some special alone time right before bedtime. You could read together, brush teeth, sing songs, whatever the nighttime bed ritual is and then you can put him in his crib.
He will cry when you first try this. So the first night, maybe you stay in his room until he falls asleep (but don't pick him up!) Use reassuring words and tell him it's bed time, and time to go to sleep. The next night there will probably be less resistance and before you know it, he'll fall asleep on his own.
I'm not a proponent of CIO, but I think it's important for him to know that he has to sleep by himself (all of you will probably sleep better!)
You can also try a toddler bed, but you'll have similar issues as you have now, when he wakes up and realizes you aren't there. He may begin to feel reluctant to fall asleep in the toddler bed knowing that you will "disappear" sometime in the night.
Good luck!