First of all Sara, I just looked at your profile and you listed yourself as a loser. You're NOT, no matter how much of a mess you think you have made of your life. I don't know if the "19" refers to your age or not, but if you are still in your 20's my suspicion is your dad is throwing money at you because he doesn't know how else to express his love and doesn't want to see you want for anything. I think a lot of wealthy families are like that. (The ones I've seen in the movies anyway.) Being your dad, I would bet big money that he really cares about you but perhaps never had a parent himself who showed affection any other way than the way he is doing it. Try talking to him about his past. He will be reluctant or may refuse. That in itself should give you a clue. I'm in my late 50's (a mother) and have a late 20's daughter who has seen ME go through a lot of alcoholic behavior. Despite that, she hasn't written me off.
The above was a bit long winded without answering your question really. What I would do is reach out to him more and try to find out more about how he was raised. By getting to know more about his background and about him today (besides the money thing), you might be more comfortable about opening up to him about your problem. YOu could then ask his advice about what HE thinks would be a good idea. He might actually bring up rehab. If not, by then you may be more comfortable in doing so.
I wish you all the best. Above all, don't lose contact with him. It sounds like he may be trying his best the only way he know how. You can try to teach him another way.