For what it is worth, we noticed some similar behaviors with DS at about the same age (the baby talk, fingers in mouth -- definitely seems to be related to his teeth, he's not lost one yet but they are uncomfortable, melt-downs, etc.). In my research, I found a lot to suggest that much of this is age appropriate, if disconcerting.

That said, hay fever did make things worse. His pediatrician put him on OTC meds several months ago, which seems to be helping energy levels.