God @harvs I feel exhausted just reading that. You poor thing. And your poor DS. He must also be exhausted.
DD2 was very similar. I remember vividly dreading coming home from hospital after giving birth to DS1 as I had no idea how I would cope with her sleeplessness. She was just under 2 and getting worse. She had night terrors, slept walked, would be awake for 2-3 hours overnight. DH travelled frequently when DS1 was tiny and I dreaded it. I'm ashamed to admit it but one night I'd be up with DS fOr about an hour when she started screaming and carrying on. I had her in my bed and was begging her to go to sleep. I even put my hand over her mouth and for a split second thought I could keep it there and she'd go quiet. Of course j didn't and it terrified me how bad it just have been to actually think suffocating her was better than what we were going through. I took her to GPs, locked her in her room. I did everything.
In the end she just had to grow out of it.
DD2 has gone on to prove herself to be an incredibly individual child. She still suffers separation anxiety and is an anxious child, but we know now she is also profoundly gifted and that probably had a lot to do with what she was going through. It was like her mind struggles to ever switch off. She's prone to dramatic mood swings and gets really angry at DH or I if we "fail" her in some way or if she feels she has failed herself.
I used to say I'd lost the sleep of a thousand newborns in the first 3 years of DD2's life.
Sorry I haven't any practical tips. I really don't know what works except time.