I think time frames are the key here. What is yours? If you are eager to begin a serious, long-term relationship with this guy, and you can't really wait for him to sort out his demons, then I'd say pass on this guy and keep looking.
He Just Has Trouble Letting Go
His time frame is clearly very slow. He has a lot of trouble letting go. He may also be wary of trusting again. He has had two women hurt him pretty deeply, pretty recently.
Therefore, now may not be the best time for him to start getting real serious with someone else. I was divorced at 23, and it took me about two full years to really be ready to commit again.
You Have A Great Foundation
On the other hand, it sounds like you two have a great foundation.
In fact, your willingness to be there during his confusing times with his exes shows a great deal of patience and love on your part. You have to decide how long you are willing to wait for him.
Tell Him He Could Be a Potential Stalker
I would be honest. I'd tell him that I think he's pining over his ex-girlfriend too long and that it sounds like a potential stalking situation. Find out what you can do to help him get over her.
But, be careful...you don't just want to be the rebound woman.
Honesty and Communication are Vital
Communication and honesty are vital here. Make sure he is being honest. It sounds sticky, but the older we get (I'm 36) the more sticky and complicated our relationships become.