Ah, another vote for keeping him close. Skin to skin regulation and physical touch is shown to help babies regulate. It's hard because you can get touched out, but if it soothes him, it's worth it. Honestly, I can't advise on carriers personally, but plenty of people I know have chosen the ergo ones. Lots of cultures baby wear untill toddlerhood it's not that unusual.
I really really wish someone had told me it was ok to treat our 2 year old when he came as more of a baby. He had so many gaps in his understanding of how to be a baby that I could have filled. Looking back at photos, I'm amazed at how tiny he really was.
Your little one is a year old, a teeny tiny baby. Plemty of kids are still being breast fed at this point. He's a baby! Independence? And independence for a kid whose nervous system is probably in tatters? Oh for goodness sake. Social workers present themselves as gods sometimes, and quite frankly out of the 6 involved with our kids transition, only 1 of them was worth her salt when it came to advice about how to actually bond with them. You need to go right back to basics, imagine emotionally you have a newborn and act accordingly. Your baby is in a position of extreme stress, for at least the second time in their life. Regression is normal and expected and nobody should be asked to do something new when they are in that state, let alone a baby. You wouldn't expect a newly widowed person to suddenly start wearing a suit and tie and going for a jog in the morning if that wasn't what they were used to. You would bring them nice things to eat to show you cared, make sure their environment was clean for them, hold their hand and watch the same film on repeat with them because it reminded them of their loved one and give them a cuddle if they were crying or emotional. Why should we expect a tiny baby to start being more independent and doing things they have never done before when they grieving and scared? Also, you can't spoil a child by giving them emotional security and comfort, no matter what form that takes. They will let you know when they are ready for independence.
Treat them like a newborn, get yourself a pair of loops earplugs (I swear to God they saved me from the screaming, you need the super strong ones if they are super loud), make sure their naps are regular and consistent, and comfort comfort comfort.
I second co sleeping if you are knackered- it was the only way any of us got any sleep, and our relationship turned a corner, particularly with my eldest. Whether that was because he was more regulated at night, or because I wasn't so bloody tired is unclear. If he rolls out, you can put towels or pool noodles under the sheet at the edge and tuck it in to keep him from rolling, or get a bed guard and attach it to the side of the bed, or even put your bed up against the wall for a bit. That's what we do when we travel and the beds don't have guards.
I would also say, don't bother offering him stuff, he probably is beside himself and couldn't choose something that would calm him down even if he knew it, and possibly doesn't really have the skills needed to self soothe if there are any sensory issues emerging. You might need to play detective, give him something, play with him and narrate how it might be making him feel, and keep a note of anything that is effective, then just do it for him. Play peekaboo and give him rattly paper, or shiny things. Look up games to play with newborns and do those. I remember being told keep Christmas barely existent, until I realised the eldest loves the lights and would only be soothed when we looked at them twinkling. The decent social worker said ' well of course, if a baby was crying you might take them to see the lights and point at them right?'. And so we tromped up and down the streets in his buggy, looking at the lights, making our hastily erected Christmas tree lights flash, watching the lights on our skin... And for half a hour the screaming and crying stopped. And what a bloody luxury that was. Even now, just yesterday, I was sat on the floor with my 4 year old putting a blanket over my head and playing peekaboo to get him out of a towering rage he was in, because that's what I would do for a tiny baby.
I would also second music as a way to set the mood. Try different genres too. I wanted to imagine that I would be a lovely classical music household, but turns out that bopping along to dad rock, sea shanties and cheesy 90's pop works best for our two because they like the strong beats and repetitive nature of the songs. Sea shanties in particular have a soothing rhythm and bass to them (when you get into the science of them, it's really interesting because depending on the job they were designed to go with depends on their rhythm and tone) and the call and response element is predictable for them. And yes, yes I was desperately down a 'how to make your child sleep' midnight internet rabbit hole when I was sat up with the eldest pre cosleeping revelations when I found that out.
However, you should also think about whether there are any underlying issues as well- would your health visitor support a referral to community paediatrics? Or might it be worth speaking to your GP? For example, lots of kids who have experienced trauma might have issues with their bowels, because food and gut health are impacted by trauma. Constipation makes plenty of people angry and grumpy, could that be an issue? Or is he waking himself up by snoring? Once we had some tonsils removed, inhalers prescribed, constipation sorted, and worked out one was lactose intolerant, our two seemed to vibe much better.
Finally, a holding hand moment to say, it will pass. The first 6 months for me were so incredibly difficult. I felt so lonely, because I had gone from my career as a teacher, where I was being social and busy every day to having to work out how to get a screaming 2 and a 3 year old to stop screaming and fighting with me, each other and the world, and literally nobody else in my life apart from other adopters got it. My family, who I thought were going to be my rock, refused to acknowledge that these kids were any different to normal, and the parents at the stay and plays were horrified at my kids because their behaviour was completely out of whack. However, it does get better if you just focus on the bonding and meeting their needs, and making life as easy for yourself as possible. You both deserve life to be easy and nice wherever possible, so do whatever it takes. Go and grab a fancy coffee, find a quiet soft play with some blocks that fascinate him for ten minutes so you can do bit of a puzzle book, whack on some cocomelon with a bit of chocolate each so that you can have a bit of a sitdown.
It's all going to be ok, you will find your groove eventually, even if it is really difficult right now.