Well, it went from bad to worse last night. DP fed him just before 2, and he refused to go back to sleep. DP said he was taking O downstairs, and I was to sleep. 
I had my reservations, given DP doesn't wake. But figured I'd hear him anyway, I usually do.
So this morning, DP tells me he never went to sleep :( O kept waking every 10-15 minutes all night long til 6 when DP gave up and got him up.
O was in the pram - so the place where he sleeps the best.
He then slept solidly this morning from 8.45-11.40 after screaming the house down prior to falling asleep.
What the fuck is going on?
I have to admit, in desperation, we tried pick up put down again the other night. Yeah. That child is strong willed. He does not give up. He cried for 3 hours and I cried for about 2 of them too. If we ever tried 'controlled crying' it would be anything but controlled, because he just doesn't stop. Ever. The 3 hours only ended because I stopped it, not because he stopped. 
DP is now in bed, he finally came to bed when O went to sleep this morning. :(
We can't go on like this. :(