If every things are set at your in-laws’ end and you are ready for it, then you have only one option left for your parents. The option is, give them a deadline; till you will wait for their permission and then onwards you will go on your way. If you do not have courage to tell this to your dad, tell to your mom; any way it will reach to him. If you have made up your mind for this marriage then be prepared to take your parent’s retaliation. This could be verbal as well as physical.
Getting married without parent’s consent is always stressful and you will keep tense about this. Only relief for you is; you are accepted at the end where you are going to stay for your life.