I wouldn't do the throw the treat to get the dog to move trick because there is something else going on . The dog would rush out scarf the goodie and then come back in a rush to bother the child .
Why would he come back to bother the boy? I'm sure it is not the dog's goal to bother the child, and as you can see from the updates.. The dog is not bullying him.
The reason why I suggested the treat was because this might be resource guarding. Once they give something up (going after the treat) then they lost their chance.. If the doorway was so valuable that the dog would go get the treat and them come back to reclaim it from the boy... Then the dog wouldn't have left the doorway in the first place.
It is trading one thing for another, Niko gets a treat for giving up the spot he was laying and the boy gets to continue on his merry way. It's not like the child will be lingering in the spot.. Hes just walking through.
In an ideal situation, you wouldn't want the dog to resource guard at all or get dependent on a trade. But that isn't the case. I think OP has made it apparent that she wants to work with Niko and make things work..
Thank you OP for updating us on your situation.
How much does Niko like his crate?
There is something I want you to do..
Make his crate the most BESTEST place ever. Feed him in there, give him treats, chewies, etc. Create a command so he goes to his crate whenever you give the word. First start next to the crate and gradually increase the distance.. Then stand outside the door and ask him to go to his crate.. advance down the hallway.. Until he runs like a lunatic to that crate!
It may take many months to be able to do it.. But if your child could say 'Go to your Crate, Niko!' and that dog drops everything hes doing and runs to his crate and waits for his reward.. It is something invaluable. When my dog slipped out the door once and made a mad dash to the pasture with horses in it.. He ignored 'Come' 'Here' and my emergency recall.. But telling him to go to his crate made him turn on a dime and zoom back inside the house just as fast as he went out.
In addition to Mind Games.. Take a look at crate games too..
Best of luck and merry christmas.