I;m with Midori. No-one comes between me and my dogs and there would never be any question of me giving them up.
I have the upper hand on you - my 3 are older. BUT, although 2 of them came to me as adults, my younger GSD was a pup when I took him on. And yes, he was bloody hard work. He could have been a nightmare, he's a huge, strong dog, very bright, into everything, bouncy, on the go all the time. That's why I had to train him, exercise him and keep him occupied mentally too. Still do, obviously.
First thinks first, if your BC is hard work, wear him out. Not just bodily (be mindful of the amount of exercise you are giving growing bones) but mentally. Take him to training classes if you're not already and invest in 1 to 1 classes if necessary.
He's a pup. He isn't snapping, he's playing, pushing boundaries and learning. He will mouth too. They do that, c'mon you BOTH knew that when you took on a BC with 2 young kids in the house.. didn't you?
You see, the problem is, we're up to our mecks in dogs in rescue, we are on our knees, we are struggling, ESPECIALLY at this time of year. And it's at your collie's age or thereabouts that people all too often decide to give up and get rid. Those in most pounds won't be there over Christmas though...
Pounds don't like paying staff Bank Holiday rates and so tend to have a clear out cull, killing all the pound dogs they legally (and sometimes ILLEGALLY) can get away with, to save themselves staff bills.
It's situations like yours which compel decent rescues to insist on meeting ALL the family and being sure that ALL the family want a dog. It's also why many won't rehome to a home with young kids.
And it's why I get a bit cross when someone is blaming a puppy for being a puppy and wants rid, as your husband does...