i left islam-i am confused

I am born in ortodox christian family, later I was on time with the jehovas whitness, later i converted to islam and I stayed 12 years in islam, I was just knowing the trueth but i still live like unbeliver do sins. Later I prayed several times, But In July this year I fully dedicated to islam my self i start praying regulary 5 times a day, i stop gabling eating pork stop drinking, before that i was alcoholic one kind. i have a problem with jinss and physical illness. Everything was great ALlah give me a wife for me as i prayed him just how i imagine, my family finaly accept my wife and my faith even they opposed at first,I was living in Macedonia after I lost my work, i recive a job invatiation in China, when i am now. In China i used to pray for less than 20 days, after that my emloyer was angry with me because i date a morrocan girl, i could not tell them i am muslim at all just a little, i was afrait not to eat pork in front of them and i made the sin i ate pork. Later i got a new room mate christian metodist and we disscuss faith with him, he was asking about islam blaming the quran and try to defend it, and all was good, He told me christian peole go and pray for ill people, they heal them by the power of Jesus Christ, blind deaf, invalid, I said muslim also heal with quran, muslim also pray for ill people... and then he told me Jesus never say to kill anybody not even if he is sinfull, no mater what that person did you shold not kill him/her. So in the Hadiths the Prophet s.a.a.s kill a witch who made witchcraft for him, the companians kill the umbelivers by juddging them to death. he asked me Why, when Jesus show love in the Gospels, I showed him all scientific mistakes in the bibble and all scientific proves in the quran, se says maybe is from the satan because jesus show loves, I also says about the apocrifical gospels and the prove for islam, he said no love, I am not sure if islam is true or not or Jesus christ is the saviour, I might make shirk and go forever in hell, i feel terible i like to kill myself once again, so much pain in me. Jesus says never kill anyone even he do sins forgive him, Can you explain me in the New Testement if there is a state about allowing killing guity people who don't reppend,