An orphan is someone whose parents have died, are unknown, or have permanently abandoned them. In common usage, only a child who has lost both parents due to death is called an orphan.
We must pay our Khums immediately to the Marje' of Taqleed or according to his permission. We can not keep part of it with us waiting for two years installments. You should give the whole Khums to the deserving persons according to permission of the Marje' of Taqleed.
No. The main condition for a man to have more than one wife is the practical justice between them. Those men who are unable to have and keep this condition are not allowed but one wife.
1. We abide to the meanings of Quranic verses and rules of Islam as explained by the Prophet Muhammad (SAWA) and his Holy Progeny Ahlul Bayt (AS), and not our own thinking or our superficial linguistic understanding which is away from what the Prophet and Ahlul Bayt have explained.
2. Khums consist of two equal parts; Sahm Imam, and Sahm Sadat. Sahm Sadat is the right of needy Sadat who ae from the family tree of the Prophet (SAWA). Allah (ST) knows that Ahlul Bayt (AS) and their families will face big difficulties from their enemies, that is why, Sahm Sadat has been ordained for the needy Sadat.
3. Sahm Imam (AS) is the right of the Imam (AS) and it is received either by him or by his deputies like the Marja' of Taqleed or his deputies now a days. Sahm Imam is used generally in serving the general poor and needy and religious, educational and social services.
Having such feelings after this incident probably happening a long time ago is a positive sign of your righteousness. Seeing that you have repented, the only thing remaining is that you pay that specific amount back.
Should you wish to sponsor orphan/s, then that would also be an honourable thing for you, or any beleiver to do.
If your question is regarding who the Wali 'Amr is, and a wali amr in this case refers to the Islamic guardian, who is the father, or the father's father, then there are few scenarios:
If the girl is a virgin, and not religiously independent (rasheedah) her wali amr can be a male who her father has appointed in his will. If the father has not appointed anyone in the will, then her wali amr is a Jurist who carries all the required conditions of Ijtihad. The Mujtahid that she selects will be her authority and her guardian. This means that the Mujtahid can approve the marriage, and hence it will be legitimate.
If she is rasheedah, and rasheedah in this Islamic context means a woman who has not been married, but is individually, socially and financially independent and she alone makes her own choices and decisions. In this case, she does not need consent from anyone.
In any of these above cases, it is crucial that family members be involved as well. For example, even though from a shar'i perspective she does not need to seek consent from her mother, or her uncles, or elders, but it is indeed morally and socially very important to do.
And Allah knows best.