1- Since she is Muslim and her father is non-Muslim, she does not need his permission for marriage (whether temporary or permanent).
2- You do not need your family’s permission to conduct the marriage contract.
3- You can have the marriage contract done directly between you and her. You don’t need a scholar to perform it for you.
4- There is no minimum for the dowry. Anything that has value qualifies. So anything that has value in the eyes of society is ok as a dowry.