Equality between one's children

Q: There are 4 sons, youngest son lives with parents, father is alive and decides to give youngest son 50% of the house share and 50% remaining to the other 3 sons. The youngest son has also purchased another house, but is living in the current one.

The other sons are not happy as they say that it was unfair for our dad to give more to the youngest, on the basis that he lives with him and in tradition the elder brothers should give youngest most.

The brother's refused the 50% share as they wanted full share, not half. Is there any sin on the father because he decided he wanted to choose who he likes to give?

Zakaat on bamboo and sugarcane

Q: I have question regarding zakat. I have cultivated bamboo on my land. Do I have to give zakat on bamboo? As far I know, the bamboo plant is not for eating so after harvesting it will I have to pay zakat?

What about sugarcane cultivation? E.g if I cultivate sugarcane on my land, it takes one year to harvest and after harvesting I have to send it to the sugar mills and I receive my money like after 2-3 months. So it takes 14 months and my harvest is almost more than 40000 mound what I have to pay? Will it count in money? 

Teaching one's child hifz at home

Q: My son started hifz class in September 2017. Before he went into hifz class he already did 4 juz at home. He started from juz 1 at the mosque as he is the youngest in his class and he was nervous. Alhamdulillah they has never been a complaint about him regarding tajweed or anything else. I feel he prays proper at home with full concentration. Would there be anything wrong in teaching him at home?

Marital problems

Q: I have two wives. I want to be just between them as much as I can. But my first wife in hindering it by getting annoying. Time and again giving me reference of Nabi (sallallahu alaihi wasallam)'s reaction of finding out the intention of Hazrat Ali to marry second time. Giving me reference again and again that you cannot be just between two wives. Asking me questions again and again why I married second time. Bringing the topic of second wife again and again. Asking me the same questions again and again for which i have answered. When i decline to answer and choose to keep quiet, so matters dont get out of hand, she does not tolerate that. The last incident again, i came home late from work tired. and after an hour or so. she said i want to ask a question, which i immediately sensed will lead to argument, so i said, if the question is baseless then should not ask. then she started giving arguments to which i chose to remain quiet and the end she said, you attitude with me makes me doubt you. At that i went to the other room and slept. I am trying my best to be fair as i can. But she infuriates me time and again, intentionally or unintentionally i do not know. What can I do to solve this.