First, let me say that one of the reasons God has given us the institution of Guardianship is to prevent men from crystallizing the Cause of God into a rigid system. Your questions are mostly along the line of trying to lay down a fixed pattern for future society, long before the time for such a pattern is ripe. Remember that Bahá'u'lláh says what is not already revealed, the International House of Justice must in the future legislate, and it can make, and abrogate if necessary, its own laws. This means not fixity in guiding society, but fluidity!
No. 1 Bahá'u'lláh and the Master mention only Local, National and an International House of Justice. There is no provision for divisional ones. Each city will have its own Spiritual Assembly, not a number of district ones. Naturally, district 19 Day Feasts can be held where there are very many Bahá'ís in one city.
No. 2 The Hands of the Cause will have executive authority in so far as they carry out the work of the Guardian.
No. 3 Spiritual Assembly is the name at present for the body which in future will be called "House of Justice".
No. 4 The Badí' Calendar will be used generally. The Bahá'í week has seven days.
No. 5 There is nothing about "ground organization". These details are left for future legislation.
No. 6 No. Such things are for the consideration of the legislative bodies in future.
No. 7 No. But `Abdu'l-Bahá stated there are other worlds than ours which are inhabited by beings capable of knowing God.
No. 8 The Bahá'í Temple in America has been dragging on, uncompleted, since 19..(figures unreadable); its completion is absolutely essential. We are builders, we have confidence in the protection of God. We cannot give up our work just because the atom bomb has been invented! This would be cowardly! The United Nations disposes of millions and millions of dollars and part of its work is to educate humanity towards peace and against war. Our completion of the Bahá'í Temple will cost 3/4 of a million; what could this sum do in comparison to the efforts of the United Nations?
The thing the German believers must do is to deepen themselves in the Covenants of Bahá'u'lláh and `Abdu'l-Bahá. Mere intellectual understanding of the teachings is not enough. Deep spirituality is essential, and the foundation of true spirituality is steadfastness in the Covenant.