I'm sure having 50% custody is pretty tricky, and it may not be possible to make changes to your schedule (or you may not want to make changes) but since your sleep issues are tied to anxiety about your son potentially waking up when he's with you, have you considered the possibility of temporarily not having him sleep at your place
I've tried. My ex wife is averse to inconvenience.
Our relationship broke down pretty much the week she decided, after co-sleeping with him for 7 months, that she was burned out and made us Ferberize him in one night. His metabolism was set on a 12 hour nighttime nursing whenever he was hungry to suddenly going hungry for 12 straight hours a night.
If they hadn't been co-sleeping and he was let to cry it out from the start I would have been okay with all this. Or at least a more gradual transition; but no, she wouldn't have it.
The first night it was my job to Ferberize him, or at least a gentler version of it where I stand in the room with him for the first couple of hours. His head was covered in cold sweat the first minute he realized what was happening as he frantically cried in the dark.
That week, watching him suffer like a little animal in a dark room on the monitor, I stopped loving my wife and became an asshole to her.
I need to do this the hard way and get over this hump.
He's also coming down with autism. This is destroying me. I need to figure out some way of helping us both, because I suspect the conditions (CFS and autism) are related.