How very difficult for all of you!
I also recommend the Elizabeth Pantley books, they've been very helpful to me.
And I agree: don't blame yourself, some kids are just bad sleepers and what works great for some will not work for you - you do have to follow your instincts, guided by your intimate knowledge of your child.
A few ideas to throw at you:
Bed time routine - at least 1 hour before bed
An earlier bedtime (Pantley reckons 6:30-7:30 is ideal time for most kids, and would agree; at least for my son anyway)
Lots of exercise during the day
Diet - could there be something he's eating that's disrupting his sleep?
The timing of his nap (ie, not too late in the afternoon)
And basically, what Mak and Doudou said
Really hope you can get some better rest soon (and I'm sure your boy needs it too) and feel free to come and cry on bb anytime you need.