This is a complex question and I took time to read it well.
You are in love with a man who you desire be your husband. You have family who has strong opinions about his worth and his work ethic. It is causing you to question yourself and your relationship. This is the issue.
The emotional rule here is actually very clear. This man will be your husband and you his wife. The future marital relationship is a lot like an image of two people slow dancing together. There are only two dancing; all others are audience members and are not in the act of dancing. If anyone tries to break in, or if anyone or anything comes between you both, the dance is over.
Here you have a problem that is resolvable via a perspective change. Yes, you are your father's daughter and also you have a family. Your father and family have a right to an opinion. However, you are an adult and they do not have the right of control. You are "dancing" with your boyfriend, (soon to be more) and parents try to cut in. The proper response is to gently remind them that you appreciate the concern but that you will make this choice. It is really that simple. No it will not be easy for you to establish your adulthood with them as it is clear that they still see you as their little girl. But:
You cannot be forced via an emotional pressure to see things as others wish you to. They can try but you will need to resist and establish yourself as the choice making person.
I would advise that you seek a therapist to gain some perspective into this issue. There is just too much control and emotion in this situation for you to be able to see this clearly. Families can be incredibly frustrating and influential, both good and bad. Here however, it is a bad influence as your adulthood is being questioned or even taken away. This is your life, not anyone else's
The key question that you need to talk about with a therapist is: What do you really want, apart from what your family wants...I think by doing so you will see this for what it is and you will resolve this issue.