It sounds like you're in a bit of a bind! And it does sound like you're trying your best to respect your family as well as trying to win a little independence for yourself.

I wonder if there's anyone outside your immediate family whose opinion your dad respects who can talk to him for you and explain that what you're asking (in regard to wanting to pay your own bills and be more financially independent) is perfectly reasonable?

If not, I wonder if you could negotiate a particular age at which he would be more comfortable to let you do your own thing.

That's not to say that I don't think you're mature enough - from the sounds of it, you're very mature, I'm just trying to think of ways that would give you what you want and keep the peace.

In terms of marrying your BF, I think as others have said, take it slow and give him every opportunity to win over your family. Not so long ago, it was common for people to marry young so that they could 'get away from' their own family and a lot of unhappy marriages ensued. So it really is worth biding your time and trying to chip away at gaining some independence for YOU first.