Translation - Portuguese-Latin - por deus abra essa porta

I think it should be : "Istam portam pro deūm aperite", but I'm not sure. What I'm sure about, is that the "complèment d'objet" has to be used at the accusative form, and that "pro" is here followed by the vocative form of "deūs". Then building of the sentence has to take care of the Latin syntax (of which German syntax is coming from) which uses this particular form : "sujet-complément-verbe"; And I'm wondering if it shouldn't be "portam istam", I'm not sure at all for that.