I really feel for you - my daughter has had trouble falling asleep since she was a baby. It can be really rough! I used to spend hours and hours trying to get her to sleep or nap. :-( Fortunately, she's better now (at 9 yrs old). She goes to sleep on her own (most nights) and sleeps in her own room all night. (My 6 yr old ds is another story...)
She doesn't have the same level of anxiety as your child, but here are some things that worked for us...
We let her go to bed later - we eventually realized that she's a night owl. Trying to make her go to bed when the sleep books said she should was just an exercise in frustration. She gets ready for bed at the same time as DS but then we let her read (or draw or whatever) for a set time. Lights out is around 9:30 - 9:45 pm. By then she's tired enough that she (usually) falls asleep quickly. So even if one of us does end up sitting with her (rare these days), it's not for long.
My husband also taught her progressive relaxation and I think she still uses this sometimes when she's wound up for some reason. Oh - and she also uses sleep sounds (rain, waves - there are a few free Android apps that have this).
For the night waking - I don't have suggestions (my DS still does this), but I like the idea of trying a separate bed or mattress in your room.
Good luck. I have found with sleep issues that they do typically improve over time (although it doesn't always feel like it).
