last time I checked Bitfinex didn't have any fiat markets, there were all USDT (attention to the last letter 'T') which is an altcoin called Tether. it is worth $1 but it is not dollar. and withdrawing it is like withdrawing any other altcoin, you just give it an address and you receive it after confirmation.
I don't use Bitfinex to be able to tell you what the minimum is but it should be pretty low since it is not fiat and the fees should also be minimal because it is a cryptocurrency not a fiat.
Yes it may be reason that conversion is not in terms of USD but USDT.I never seen it so closely.So now I can transfer it like other coins.