I can't tell from your post - is it your dad or your FH that thinks you are moving too fast?
Also, when you say that your FH thinks that you have way more important things to focus on than the wedding, what is he referring to? Finishing school? Becoming financially independent? Building a stronger relationship?
I agree that you have much more important things to focus on than the wedding. We all do. As important a day as your wedding will be, it is only one day. Having a perfect wedding at age 20 will not help you much when you are broke and desperate at 22 because you have no money to finish school. I'm really not trying to assume anything about you or accuse you of not knowing what is really important, but I can't stress enough how important it is to be PREPARED for marriage. At your age, I really do think that you would benefit from a few years of preparing for adult life, let alone marriage. Perhaps you are financially independent (I'm guessing not, since you are expecting your dad to pay for much of the wedding), but unless you invented Google or MySpace, I doubt that you're making much money, even if it is enough to pay your bills. Becoming financially independent is hard and money is one of the top things that couples fight about, so I really worry about all our young brides. On their own, either of those things are hard to deal with - it just doesn't seem like a good idea to me to combine the two, if there is any way to avoid it. Anyway, perhaps you don't want my opinion, but your FH seems to share it by saying that you have more important things to focus on, so it may be worth thinking about some more.
On the 'he thinks we're moving too fast thing,' I mentioned above that I'm not sure whether you're referring to either your dad or your FH. Either way, it may be a good idea to think about it some more. If it's your FH saying that, you may want to slow things down and either don't move in together for a while or push back your wedding date. Remember that he is the other half of this relationship, so you don't want to push him into something that he is not ready for. I know you said that he proposed, but we've seen women on the boards who find out (sometimes months or even years later) that their FHs felt pressured to propose, despite not really being ready. If he's telling you that he thinks you're moving too fast, listen to him.
If it's your father that thinks you're moving too fast, it might be a good idea to listen to him, too, particularly if you're counting on his financial support for the wedding. As much as they annoy us sometimes, our parents really do have our best interests at heart. Your father also knows you well- perhaps he is seeing something that you haven't noticed. Or perhaps he just thinks you're too young and is worried that getting married will keep you from pursuing your own dreams. It's worth a heart-to-heart with him, I think. Just to give you a personal anecdote, my dad and I had a similar heart-to-heart when I first got engaged. I am 27, so it wasn't an age issue, but I have been working on my PhD and my dad was afraid that planning a wedding would distract me from my studies, something that he knows I am passionate about. He told me how proud he is of me for my ambition and hard work - but he was worried that I wouldn't be able to follow my dreams after getting married, since I'd have to compromise with my FH about where to live and whether to take every opportunity that comes my way. I explained to my that my FH is just as proud of me and 100% behind me about my career choices. Perhaps my future may end up different than I expect it to be, but my FH will not let me give up on my dreams, either. So anyway, the point of telling you that was to explain that your parents may have a completely different perspective than you, but it is worth talking to them about it and thinking about what worries them, since they do want the best for you.
