Now I'm blabbering (sorry ) - so what works for you when you hit that wall?
prayer!!!

a friend of mine used to play "whats the worst that can happen" and think 'well, I might just be awake for the next 5 hrs, ok, I can deal with that'

its really hard being sleep deprived... I dont have any advice - but hang in there, sounds like youre doing a great job with your lil man.