Does collecting saliva and swallowing it break the fast?
Swallowing collected saliva does not break the fast, but it is an unnecessary and meaningless act.
A group of about thirty young men will go to a farm on Friday. Is it permissible for one of us to deliver the sermon (*khuṭbah*) and lead us in the Friday prayer, or is it necessary to go to the nearest mosque?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
The Friday prayer (Jumuʿah) is not obligatory upon a traveler, whether his journey is long or short, if he leaves his place of residence before the time of Fajr begins, according to the Shāfiʿī school. If, however, he sets out on his journey after the Fajr adhān, then he is obliged to perform the Friday prayer, whether in his own town or in any town where the Friday prayer is held.
It is stated in Bushrā al-Karīm (Vol.1/p.383), one of the books of the Shāfiʿī school: “[The Friday prayer] is not obligatory upon a traveler on a permissible journey, whether long or short, if he departs from his place of residence before dawn.” End quote.
Accordingly, if you set out on your journey after Fajr, you are obliged to perform the Friday prayer in the mosque. The same applies if you set out after that, since you would not have fulfilled the conditions for the validity of the Friday prayer, among them: that it be attended by forty men who are free, adult (bāligh), sane, and settled residents of the place where Friday is held. It must be held within a cluster of connected buildings, whether a city, a village, or a district (liwāʾ), for what counts is the gathering of the buildings. And Allah Almighty knows best.
Is it permissible to offer prayer at home, or should it be offered in the mosque?
All perfect praise be to Allah, The Lord of The Worlds. It isn`t preferable for the man to pray at home as praying in the mosque is twenty seven times more rewarding. Therefore, this should motivate him to offer prayers in the mosque. And Allah Knows Best.
Is it incumbent on a father to cover the marriage costs of his son if the latter couldn`t afford them?
The son should seek the help of his relatives in order to convince his father to do the aforesaid, and the father should make sure that his son doesn`t commit fornication through helping him to get married, and Allah will reward him for doing so.