Like everyone else said, I wouldn't rub the dog's nose in his poop.
Apart from the advice the others have given, I would try to do the following:
- Keep an eye on the dog's bathroom schedule. It's likely that he'll relieve himself at similar times. Then, around the time that you know he'll go, take him out.
- Take him out for walks after meals, it's more likely that he'll poo then.
- Try to keep an eye on the dog as much as possible. There's the possibility that he'll act in a particular way before relieving himself, so if you're able to spot that, you'll be able to take him out.
- If you take him out for a walk, and he hasn't relived himself, do the whole routine like you were going back inside the house but at the last minute stay outside. I think this would work in the case where your dog would relieve himself immediately after coming back from a walk.
Of course, give lots of praise and treats when the dog does his business outside.
I know the points above may seem like a lot of work (or at least, a lot of dog-watching), but I believe that all the time and effort you invest early on is time and effort that you'll save later on.
I wouldn't really scold or punish him for relieving himself inside; I honestly believe that dogs have no special interest in doing so, and as the others have said, they like to keep their living/sleeping area clean. If the dog has an accident inside the house, I'd recommend cleaning it with water mixed with bleach to kill germs and get rid of the smells. I don't like the smell of bleach at all, but it worked much better than cleaning it with nice-smelling cleaning products.
We more or less followed the points above (except for the last one, it didn't occur to me at the time) and in just three days our dog was housebroken, excepting the odd accident. She was a bit older than yours, though, she was four months and a half.
Finally, do not focus on the apparent distinction the dog makes between you and your husband. Dogs are very sensitive and intuitive about a person's feelings, and if you feel weird/worried/resentful the dog may pick up on it and act differently. I'll give you a very silly example that has really happened to me: our dog Nix would keep quiet most of the time but bark when I was on the phone. I didn't really get it until I realised she usually did it with phone calls which had to do with work or with people I didn't know. Conclusion: I was a bit nervous on these phone calls and she picked up on it.