Firstly, well done for reaching out, OP.
It's hard to take criticism at any time, but when it's in relation to our children, the most precious things in our lives that we are putting our whole hearts into, it's the hardest thing in the world. Well done for taking these comments on board.
Secondly - do not compare him to other children. Some of them stand really nicely, and are happy to wander along holding a parent's hand. Others want to run around and see what this does and what that does, and don't understand the concept of danger. It doesn't mean there's anything wrong with either.
What stands out to me from your posts is that you and your son have become disconnected. There have been a lot of changes in his short life, and it's got to be hard for him.
I think you know now that you need to bring him some toys downstairs to play with. 'Ooh, DS, DD and I have missed you while you've been at nursery today. Shall we go and get 2 toys and bring them down to play with?' Try and engage him with playing with his sister, but bear in mind he may not want to - he has had to share toys all day at nursery.
If he starts to get upset, stop whatever you're doing, get down to his level and talk to him. 'DS, you seem to be getting very frustrated/angry/sad. Are you tired/hungry? Do you need a cuddle?' Then discuss with him what you will do next to fix it. Things like this will help you to reconnect, and will help him stop feeling he has to fight with you to get some attention.
Also, try giving him some responsibility: 'DS, I need to cook tea now. Can you get the knives and forks out.' 'I need to load the washing machine, can you pass me those clothes to put in?'
Good luck OP. You can do this, because you want to improve your relationship.