This is best consulted with a christian psychologist, but my advise is not to push him away. Love him like you always have and support him to consult professional christian help that would guide him trough this. If need to tell him you would accompany him to this professional help. Do not accept his actions, love the person, if he wants you to accept his partner or something, tell him you do not accept this and that he please understand you. Also tell him that you will pray for him that God may guide him trough this hard times. He is your friend, do not push him away now when he needs you the most.