1. Kantians support the idea that everyone achieves the maxim for themselves. It is obvious that the jews will be the tool of that solider. If we try to lie to the solider, we can protect the innocent people and our maxim is to help them survive. From these two ideas, Kantians will agree that it is moral to lie to the soldiers.
2. I am not really sure if this corresponds to the Formula of Humanity. it is obvious that we lie to save innocent people's lives and the idea of the nazi is not moral. Thus what we do is moral. However, we used the officer as a tool, which is immoral.
3. There will be a big danger if we lie. If the officer finds us cheating them and our lies reveled, they will kill us and the jews immediately, which will risk all of our lives. In that case, our maxim will not be acieved and innocent people will die.