Hello again. Just an update for all the wonderful people who offered advice here and are following the thread or read in the future.
We adjusted her clothing and the air conditioning (no thermostat here, it's 35°c) and made sure she wasn't sweating or cold at night. No difference. We tried co-sleeping again but she wouldn't even let us get her into the bed, even after over an hour of pacing, bouncing and singing. She just instantly started flopping around, sat up and started screaming again. She's got all 8 front teeth now so she's on a teething break and she's eating really well, 4 times a day, and has a schedule designed around her (so she has the recommended amount of nap day time sleep and is not over or under tired for bed) that we follow really well. She also has a nice bed time routine and a calm sleeping environment. She never watches screens and we reduce stimulation before bed time. She only uses a dummy at night and we leave multiples in her bed because she can find them and replace them on her own now. We tried gently breaking the dummy association but this too just resulted in non-stop wailing. We've done everything.
And then it got worse!!! For four nights in a row, after writing this post, she had us awake from 1am to 6am pacing, bouncing and singing. This following two wake ups prior. The whole time, tense and twitching. Every time we tried to put her down she'd wake instantly or we'd get 30 minutes max. Neither of us slept. The morning lie in with the help of her grandparents was barely taking the edge off and I was losing my mind.
We felt that the movement had become an association so strong that she couldn't sleep at all without it, but it was simultaneously blocking her deep sleep, and it couldn't be broken in any gentle way. We had already tried to gradually reduce movement but it backfired. By this point we realised that if we didn't stop it would go on for far longer than we could possibly survive, soon with no help, and it's completely inhibiting our ability to enjoy our time with her. No one was benefiting. So, knowing that we had tried everything to be more gentle and acknowledging our own limit, we decided to go with the Ferber method once more. This was our experience:
Night 1: cried twice for 20 minutes (like a banshee), and one squeak that went no further (she found her dummy). Slept from 12-6am for the first time in her life (she had never crossed 3hrs before)
Night 2: slept in 1 minute initially. Cried for 20 minutes once around 10:20pm and 10 minutes around 4am. Some of this was pretty awful. Cried for 1 minute in between (probably dummy). Didn't wake until 7:40am also for the first time in her life (she liked 5:30 - 6am wakeups).
Night 3: Again 1 minute to sleep (stopped before I left the room). 18 minutes around 3am and we woke her at 7am.
Night 4 (current): again slept in 1 minute. So far nothing...
The first naps (same method) involved a little crying but very little. We always sing to her and rock her until she has heavy eye lids and then put her in her bed. She also fell asleep in her pram for the first time since she was tiny. And during the day she's the happy, energetic, extremely entertaining baby we love and now have more energy to enjoy and care for.
I'm writing in all this detail because we are a couple who have done an immense amount of research, followed two sleep programmes, seen sleep disorder specialists (who told us they had nothing more to suggest) and all manner of medical professionals (it was a bad birth). I have overcome massive psychological challenges and unimaginable sleep deprivation to make our baby feel better attached and more secure. There is a lot of resistance to CIO methods. I understand why. We didn't want to go there either. But, honestly, most of the advice out there is aimed at an average baby. 'Promised 'phases' never ended. Magical milestone ages or skill sets made little to no difference or worsened things. For us, all of the little slow tweaks cost sleep and mental health and never gave more than a few days change - if at all - before worsening again. Most of the people we spoke to, whether friends, family or professionals - unless they spent a night with us - just assumed we were exaggerating. Babies cry. Babies wake a lot. And new parents struggle. But we had never met a baby as challenging as ours. It made us feel very alone and hopeless.
I wrote my post on here in a moment of desperation where I had had to abandon ship, crying, leaving the once again screaming baby with my husband, to go for a walk so I could breath. I hadn't expected such a response or so fast. You clarified last things I could try, gave me hope and emotional support and finally gave the encouragement we needed to take this step. It's only the 4th night and we have two big moves coming up so we expect regression, but it has been so much lighter than we had expected (we expected 1hr of banshee screaming with a limit of 2hrs, several times a night), she is sleeping much more and doesn't seem at all marked by it in her day time behaviour. We feel hopeful and happy for the first time in months!!! And a lot less tired!
So, everyone is entitled to their opinion, but from my side, if you are a mother/father/parents struggling with this kind of baby, feel that you've tried everything but nothing works, but are still on the fence about CIO methods - then just try it. You can always back out. It might not be kind but neither is the alternative.
Once again, thank you so so so much to the people who wrote here and gave any kind of support whether advocating CIO or otherwise. It made the world of difference.