All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
When a person dies, his estate becomes the right of his heirs. Allaah The Almighty Says (what means): {For men is a share of what the parents and close relatives leave, and for women is a share of what the parents and close relatives leave, be it little or much - an obligatory share.}[Quran 4:7] Allaah The Almighty explained these shares in the Quran and so did the Prophet, sallallaahu ‘alayhi wa sallam, in the Sunnah. It was narrated on the authority of Abu Hurayrah that the Prophet, sallallaahu ‘alayhi wa sallam, said: "Whoever left an estate, it goes to his heirs." [Al-Bukhari and Muslim] Hence, there is no share for your paternal uncle in your father's estate due to the presence of the deceased's son.
As for your uncle's claim that he spent money for your father's education, he has to provide evidence that he actually spent on your father and that the money was given to him as a loan. If your uncle looked after the land all these years with your permission and the permission of the heirs, he is entitled to the wages of a person who does the same job unless there was an agreement between you and him on another amount of wages or he volunteered to take care of it. If he took care of the land without permission of the heirs, he would be considered a usurper and would not deserve any money. In any case, the land does not become his property by means of looking after it.
However, we advise you to seek help of righteous and virtuous Muslims there; perhaps they will achieve reconciliation between you. If this is not possible and there are Islamic judicial bodies specialized in investigating the issues of Muslims, you can file a suit with them. Besides, it is not permissible for the Muslim to resort to courts that are based on man-made laws unless the Islamic courts fail to find a solution.
On the other hand, a Muslim is not allowed to take what is not his right even if the judge ruled in his favor. That is because the ruling of the judge does not make an unlawful thing lawful nor does it make a lawful thing unlawful. It was narrated on the authority of Umm Salamah that the Prophet, sallallaahu ‘alayhi wa sallam, said: "You people have disputes and come and ask for my judgment. Perhaps someone amongst you can present his case in a more eloquent and convincing manner than the other. Beware! If ever I give somebody something of his brother's right based on what he said, then he should not take it as I have only given him a piece of fire." [Al-Bukhari and Muslim]
Allaah Knows best.