My sympathies to you, it must be hard. I think I would ask for some help form your MCHN. This is obviously taking a toll on you all. My sister had a similar problem, her DD is now almost 6 and she still has problems getting her to sleep, sometimes when she visits mum she won't go to sleep, she cries and carries on and keeps coming out of the room, eventually my sister goes in and strokes her head and gets her to sleep... Well in my opinion that is waaaay to much... 6 years of fighting to get your children to sleepp... AHHHHHHH!!! LOL
I am sure there is help available you just have to find it. As Kellee said, it may seem harsh, but what ever you try will be worth it.

Tanya