Re: At my wits end with sleep issues...
Have you done a sleep study?
My DD was about 3 when she started waking up again at night. Like seriously waking up - every hour nearly. I was 30+ weeks preggo and exhausted. Because my DH had just had surgery for sleep apnea we had her tested as well. Thankfully she did not have an apnea, but she had a condition where she was not transferring from one sleep cycle to the next appropriately. Normally you wake slightly during the transfer and go back to sleep without being aware of it. She was waking all the way up and becoming disoriented. It was related to the night terrors that run in my DH's family.
Unfortunately, they told me there was nothing to do besides ride it out. Most kids outgrow it by age 5 though a few progress to sleepwalking (which she has not and she is now nearly 6).
I would also suggest trying melatonin. It did not work for our issues, but I've known several people that it has worked really well for.