It's not really letting it go, it's taking a much needed break for some perspective and regrouping - even the troops in war draw back on a regular basis! We aren't giving up and neither are you. But you are doing everything you can as it is so really don't beat yourself up Laura, you truly have your boy's best interests at heart and that's all anyone can ask. I do believe the doc has a point that he will grow out of it at some point, I know it's no consolation and doesn't help you now, but at least it can help to know this situation is temporary. Also he's thriving and generally happy, it's the same with Finn, he could be sooo much happier if he had better sleep - we've seen the difference in him, but alas it's not in the cards just now. He does what he does, and we are working against genetics at the moment.
We're here though, if you need to run anything by us, large or small. It makes me sad that you feel your people IRL are abandoning you, this is when you need them the most!
I don't want to give you the wrong end of the stick here, but I wonder if some CBT might be helpful for you, just so you can better deal with this chronic illness and sleep disturbance issue? Is there some kind of support group for parents of kids with his immune disorder? Might it be helpful to check with those parents to see if sleep is wonky in their kids too? Hugs Laura, you are really brave.