The gates of hell will NOT prevail. Unless scripture is wrong (which I do not believe!). It may get a bit rough, but they will not prevail.
I am so sorry to hear about your father :( , my prayers are with you. Jesus knows his heart, and your intention to get him last rites. Be at peace knowing that. May God hold you and your precious father in the palm of His hand, and grant him heavenly peace.
Thank you.