In this sentence you want both sentences in the same tense - the simple past. And you also need to use the conditiinal in the second half of the sentence as you have an 'if,' clause in the first half: 'I knew that, if I told him the truth, he would get angry.' If you want the sentence in the future tense you could say. 'I know that he will get angry if I tell him the truth.'

The first one is right except you use the past tense. I knew that if I told him the truth he would get angry with me. Context will also change things, if it's a conversation that has not happen you can also say I know that if I tell him the truth he will get angry with me. Again context is important.