I'm going to post a note that's saved on my phone, so apologies its not personalised to your situation but I think it might help. Super nanny method absolutely did not work for my stubborn daughter and also I found it really hard to keep my cool doing it for hours on end, when u was already seriously sleep deprived myself.
Our main issue was night wakings rather than bedtime, my daughter would wake at 1:30am like a clock and not go back to sleep, sometimes at all. In the end (after 1yr) we got a sleep consultant to help and this is what we did.
Bedtime passes.
Start with a family meeting, draw up some sleep rules, get your child to suggest and draw them to give them some ownership.
Make loads of tokens together. I mean loads. If the child gets up at bedtime or calls you in the night then that's absolutely fine and allowed, but costs 1 token. Put them in a pot by their bed. If there are tokens left in the morning, the child gets a reward.
We've used penny sweets to start with and then moved on to playmobil. I bought a camping set and split it all up, put the names of all the bits in a pot and Daughter got a new piece at random every morning she had tokens left.
For the first few nights the child needs to succeed. So you need more tokens than they will use. My Daughter used more than 30 the first night. When they're in the swing of it, start to gradually reduce the number of tokens. It took us a few weeks to get down to 6. My daughter started to fail a few times and had to try. We got stuck at this level a while. Eventually we got down to 3 and at some point the system was gradually forgotten. 30+ night wakings down to 1 or 2 was a lot bloody better.
You can look this up, I believe it's called bedtime passes and there's a few articles out there.
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And another thing I wanted to share is that my sister ended up on the same position as you with her 3yo when she had newborn twins. They did have to be more consistent and firm and return him to his room in tears a few times. They also improved his bed, got a Nightlight and a yoto player, things like that. I don't think there was one answer but gradually things have improved.