Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
May Allah reward you for your enthusiasm regarding keeping good relationships and refraining from bad conducts and immorality. May Allah increase your zeal in doing so.
You have to know that forgiving your boss, and performing a good deed in return for a bad deed, as well as reconciling, are conducts that you should keep high. Allah is able to make the relationship between both of you better even after an instant. Allah says:"Let them pardon and forgive. Do you not love that Allah should forgive you? And Allah is Oft-Forgiving, Most Merciful. "(An-Nur 24:22)
And you have to know that Allah promised a great reward for the person who forgives the mistakes and shortfalls of his brothers, Allah says:" And let not those among you who are blessed with graces and wealth swear not to give (any sort of help) to their kinsmen, Al-Masâkîn (the poor), and those who left their homes for Allah's Cause. Let them pardon and forgive. Do you not love that Allah should forgive you? And Allah is Oft-Forgiving, Most Merciful. (An-Nur 24:22)
Also Allah says:" The recompense for an evil is an evil like thereof, but whoever forgives and makes reconciliation, his reward is due from Allah. Verily, He likes not the Zâlimûn (oppressors, polytheists, and wrong-doers, etc.)". (Ash-Shura 42:40)
Allah further says:" And verily, whosoever shows patience and forgives that would truly be from the things recommended by Allah." (Ash-Shura 42:43)
Allah also stated the characteristics of the people saying:" Those who spend [in Allah's Cause - deeds of charity, alms, etc.] in prosperity and in adversity, who repress anger, and who pardon men; verily, Allah loves Al-Muhsinûn (the gooddoers)." (Aali Imran 3:134)
The prophet (sallalahu alaili wa sallam) also said regarding forgiving: "Sadaqah(Zakah and alms) never decreases wealth, and the more a persons pardons people, the more Allah raises him in status, and the person who is humble for the Sake of Allah, Allah will raise him in status," reported by Muslim.
You have to advise your boss with the juristic etiquettes of advising, like choosing the best words, as the good words are sadaqah. You should not advise him in public, as it is better to do so secretly, because giving advice in public is humiliating to the person. Try to choose the best ways and means in calling him (to Islam), you can, for instance, give him some tapes and booklets which talk about backbiting Muslims and being unjust to them, and similar things which you noticed him doing. You can also agree with an Imam to talk about this subject in the following Friday Khutba, and so on.
But do not become angry. Abu Huraira narrated "that a man came to the prophet and said to him "Advice me "The prophet told him "Do not become angry;" the man repeated the same question. The prophet replied with the same thing several times: "Do not become angry." reported by Al-Bukhari.
As you know, when a person becomes angry, he loses control of his/her self. He might act in a way that he would later regret.
We ask Allah to enable us and you to do whatever He loves and He is pleased with.
Allah knows best.