Praise be to Allah.
We appreciate your keenness to honour your parents and to make good reach them. We ask Allah, may He be glorified and exalted, to decree reward for you and to join you with your parents and all the Muslims in Paradise.
There is no difference of opinion among the scholars that the reward for charity may reach the dead if the one who gives the charity dedicates the reward to them, especially parents. Similarly, there is no difference of opinion that du‘aa’ for both living and dead will bring them goodness and mercy if Allah, may He be glorified and exalted, accepts it. A number of hadeeths in the saheeh Sunnah bear witness to that. This has also been discussed in detail in a number of questions on our site. Please see: 12652, 42384, 102322.
It is permissible for the one who gives charity to intend that the reward for his charity be divided between him and his parents into three parts, whether they are alive or dead, because the reward is the property of the giver, and he may give all or part of it. For example, if he gives it to four people, each of them will get one-quarter; if he gives one-quarter and keeps the rest for himself, that is permissible, as is the case if he gives it to someone else. Quoted from al-Rooh by Ibn al-Qayyim (p. 190).
In the answer to question no. 20996 we quoted from Shaykh Ibn Baaz (may Allah have mercy on him) that it is permissible to give charity on behalf of both the living and the dead.
But we should point out what is best, which is to do righteous deeds for yourself, and let the reward be all for you, and to make a lot of du‘aa’ for your parents. This is what is best and most perfect. See the answer to question no. 42088.
With regard to all other recommended acts of worship, such as fasting, Hajj, ‘Umrah, reading Qur’aan, reciting adhkaar, treating people kindly and other righteous deeds, the scholars differed as to whether the reward for them reaches the dead or not.
Ibn al-Qayyim (may Allah have mercy on him) said in al-Rooh (p. 170)
The view of Imam Ahmad and the majority of the salaf is that [the reward] does reach them. This is also the view of some of the Hanafis.
That was stated by Imam Ahmad - according to the report of Muhammad ibn Yahya al-Kahhaal. He said: It was said to Abu ‘Abd-Allah: Can a man do a good deed such as praying, giving charity and so on, and give half of it (its reward) to his father or mother? He said: I hope so; or he said: Everything of his charity and other deeds will reach the deceased.
He also said: Recite Aayat al-Kursi three times, and Qul huwa Allahu ahad, and say: O Allah, the virtue (reward) for it is for the people of the graves.
The well known view of the Shaafa‘i and Maaliki madhhabs is that it does not reach them. End quote.
We have previously stated on our website that this second view is more likely to be correct, that no reward for righteous deeds reaches the deceased unless there is a text to indicate that it does reach him, such as charity, du‘aa’, Hajj and ‘Umrah, because Allah, may He be exalted, says (interpretation of the meaning): “And that man can have nothing but what he does (good or bad)” [al-Najm 53:39].
See also the answer to question no. 46698.
With regard to paying off haraam wealth on their behalf, haraam wealth, such as that which is stolen, seized by force, or taken by means of trickery and so on, two rights should be taken into consideration: the first of which is the right of Allah, may He be exalted, which was transgressed by committing a haraam action; the second is the right of the owner of the wealth, which was transgressed by taking his wealth unlawfully.
If the wealth is paid back to its owner, we hope that the rights of the owner will be restored thereby. But there remains the right of Allah, may He be exalted; this can only be dealt with by repentance or the forgiveness of Allah to the wrongdoer.
With regard to the du‘aa’ that you mentioned, there is nothing wrong with it, but do not adhere to reciting it a particular number of times, and strive to offer du‘aa’ as much as you can, without limiting it to a specific number or believing that it has any specific virtue.
And Allah knows best.