Oh, DG, you poor thing. Hope you're feeling a bit less terrible this morning. Does he want to feed when he wakes? Can you start going for some kind of minimum standard? e.g. you feed him 4 hourly, but not shorter than that. The other thing that worked for me and DP when T was absolutely horrendous was doing 1 hour shifts, and then 2 hours when he got a bit better. Eventually we had the night split into 2 (I did the first half, he did the second). It meant that no matter how awful it was, we could count down the minutes till we were back in bed and resting again. Even though our house is so tiny that you can hear everything - a loud ipod was a godsend!
The more I speak to (and read about) other babies, the more convinced I am that how you parent has very little to do with how your baby sleeps. I think if you have a good sleeper, all the co-sleeping/feeding to sleep in the world isn't going to give it bad sleep associations - I have a friend who has the perfect sleeping baby and she does all of this, but if she isn't there, the baby will close his eyes and nod off on the playmat, highchair, anywhere. Conversely, you can obsessively do all the right things - put them down awake, not feed to sleep, not co-sleep, blackout blinds - and still have a crap sleeper. We were obsessive about doing all of that, and T slept no better (worse, if anything) than he does now, taking all his naps in the pram and quite often having his cot jiggled to get him to sleep.