I'm so sorry for your loss. your concern for your father is quite natural ,but don't be panic becoz the time decided by Allah and no one can change it. of course it is difficult to endure it but you are not responsible for this all. the time for your marriage and time for your father departure is not what you decide. I hope you get my point. all you can do for him is to pray for him .Many prayers for you and for your father .