Update: He doesn't go in the house any more, thank the good Lord; however, we're still having issues with him going in his sunroom. This new house we bought has a fairly large sunroom we've given Link. It beats the pants off of any dog house I've ever seen, but I think it's a little too big. If we leave him home alone, sure enough, he'll go inside that room. I guess he considers that outside. I ended up fabricating a crate out of that roll up fencing that only has an exit out through the doggy door in the wall, and that works well, but I'd like for him to have the whole room and just use his door for when he has to go.
P. S. Link contracted Parvo back in October. Scary story short, we nursed him through, and oddly enough, that may have helped with his potty training.