That just makes me realise what a bloody awful parent I am that I can't even support him through this grief.
You’re not an awful parent, you’re a very new parent to this little one. This is very hard work. It can absolutely floor you because every adjustment he’s having to make you’re trying to make too, while also parenting a new person, while also seeing every single thing in your life changing. I remember someone saying that she spent the first 3 months thinking she had lost her mind - she was the only friend who had adopted that was honest about how hard it was and I clung to her words like a life raft in the early weeks and months.
Anyone caring for your child would be experiencing similar things to you. There’s a way through but it starts with not expecting too much too early on. You’re still settling in - he’s going to grieve, you can’t change that so take away any expectation that you can stop him hurting. You can be there, you can hug when he allows you, you can play and help him keep occupied, you can build relationship with him. Literally everything else will come with time.
If he’s eating with his hands, give finger food and lots of baby wipes, if he’s using baby talk, talk to him in the same way (and feel a complete idiot - I used puppets so I didn’t feel quite so stupid), if he hugs, accept him and offer/ask for hugs. Throwing and catching type games are good for building connection, so are things you can do alongside - Lego kits have been excellent for this in our house, we also pull out the recycling bin and make models using boxes, cartons etc - it doesn’t need to look like anything but the cutting, sticking, colouring is good. Get outside as much as you can, long walks (does he like sticks, my son still collects sticks everywhere we go), if you can get to a park do it, the swinging, rocking, jumping actions all help to self regulate.
I had visions of my kids colouring, doing crafts, jigsaws, reading etc but my kids just won’t do it - I’d spend ages setting up this fabulous craft project only for it to end in chaos and frustration. It’s hard but I’ve learned to not fret about it, we have active games, dancing, throwing, nerf guns etc my kids aren’t sit quietly kids - we use screens for quiet time.
Please don’t lose heart, if there’s anything I can help with, pop me a message. You’ve got this.