Definitely get a crate. It’s honestly the safest option until the puppy learns boundaries and even after tbh
A crate for sure is the best option. You could also try placing a blanket over it so the puppy and your son can't see eachother needed.
Nails clip them nails their like razor blades at that age. I’d personally start create traing him but you can’t leave him in there all day. So it will be one task on let the dog out and for fourth
Maybe get a crate so when you need time to do tasks around the house the puppy is in his own space. Especially when you can’t have eyes on the both of them.