Hi RobotPrincess:- Gosh it is tough isn't it?
I was thinking that I would try to introduce some sleep associations (my DS uses a dummy and a 'blanky' - but you could also use music or aromatherapy). You could introduce them at night when your DS does sleep well and then after a few days transfer them to the day sleeps. And I would also try a short nap routine eg. change nappy, strip to singlet (if it is hot), tell them a story while they are in the cot, a short lullaby. I usually hang around quietly in the room and tidy up or put some clothes away or go in and out of the room. Just so he knows I am still about.
If you give them him that time to unwind then he may sleep better. (we then follow a no cry routine of rocking if he cries, put down in the cot when calm & sleepy but awake, repeat if necessary but that rarely happens. The reason we put him down awake is so he gets used to actually going to sleep in the cot and waking where he went to sleep)
HTH.