Hmm i am 42 and expecting dc2.
I tried probably everything you have tried. I read books, spoke to other mums, spoke to health visitor friend, GP, and tried all things for prolonged periods.
CC for a month, ignoring, routine was strict to the minute for the whole 5 years that he didnt sleep.
Did try later bedtime, but without fail, he would wake 10-12 14 times a night and be up for the day between 4am-5 am every single day.
If the clocks went back/forward it was worse, summer-getting light early was worse.
He had colic, then croup which meant entire nights of no sleep at all as the croup was much worse at night.
I also worked night shifts at that time, so would be up all night, then all day then went to work. DH claims he woke maybe 3-4 times a night for him during my night shifts, but still would be up with the larks for him.
Horrendous torture together with a very boystrous, inquisitive and hyper child in the day, i couldnt take my eyes off him, couldnt leave him alone in a room till he was 6-7 as he would reak havock, distructive and into everything.
No, i did want a couple of children, but my ds put me off any more, also could never understand why any one else would want to put themselves through it!
Of course everyone elses kid slept throught he night, behaved lovely and were angels compared.
So i have placed an order for dc2 to be a sleeper, calm, laid back little thing.....wish me luck
Kinda know what to do if it isnt though, prepared and willing.