Hi, I haven't read the whole thread, but did read OP query.
My ds1 did the wake up at 5 and start the day thing too... I was exhausted as he was still feeding all through the night as well...
I tried all sorts of tricks to get him back down but eventually gave up and accepted it.
Sorry might not sound like much help, but what I did do, I hope you will find helpful, was give in to what seemed his natural rhythm at the time....
So we would get up, have a change and go upstairs. I created a safe play area (used one of those baby gates from babydan that can section off half the room). I baby proofed it and put toys and pillows in there... And a futon for me! I turned on some baby music and We both went in and I sort of nap rested for the first hour / hour and a half while he played.
He was happy. I felt guilty and awful for awhile, but chose to look at it like this- I wasn't coping and was exhausted. Many parents let their children play safely in their cot or play pen. I just simply created a space big enough for us to be together.... this way I could hear or respond if he needed me.
I wouldve let him play in cot but he wasn't happy in cot and wanted to be "up". Cot was in our room and DH needed to get the sleep for work.
After i did this, I then started having a little more energy during the day and tried to get him out more in the stroller, basically just tried to find new ways to stimulate him and found that after a few more months he gradually slept later and later.
This seemed to be at the same time I was also getting his naps more in line ( is your little one getting enough naps?).
For awhile it was a 5am start..... Then 6.... And now 7. Never got him later than 7, but it's so much more civilised than 5.
At age 22 months he started waking early again. We got a grow clock. He still won't go past 7, but at least he went back to a 7 am start again with the help of the clock :)
Hth x