But what is the difference here between "de" and "el"? Is "el" more emphatic?
el is like "out of". It's marking your point of origin. For instance, if you want to tell someone your country of origin, you say "Mi estas el Usono."
de is simply "from" or "of". It's a less lasting or permanent point of origin.
That is unless there's some nuance between this and the German "von" and "aus" which I'm basing this on.
May I ask in what way "I go from the house" is grammatically incorrect? To go is able to accept any preposition of motion, such as to, out of and, as in this example, from.
I think, that what you mean is that, to you it sounds idiomatically incorrect, e.g. it's not something commonly heard. Nevertheless, it makes grammatical sense, and even sounds like the sort of thing I would say.
So "I go from the house" is very much correct English, it's just not the sort of thing that is generally said.