Too long for comment:
It's unclear what your idea of the Forex market is but, generally speaking, FX is an interbank market. So you connect with the bank(s) of your choice and be done with it. In my experience not a lot of banks offer FIX trading though, only FIX STP and Drop Copy to your back and middle office.
Then again there's ECNs like Fastmatch where banks and ordinary clients can connect and provide or take liquidity. Most of these ECNs primarily support their own binary format and many of them offer market data and/or trading via FIX as well (Fastmatch, Dukascopy, etc.)
As for pricing, in any case it's all bespoke: Banks expect you to trade a certain amount per month but formally don't charge for using FIX (if they support it in the first place), ECNs typically charge you (or pass on) connection fees, there's no formal charge for FIX either.
So in short: If you don't plan on actually trading FX the minimum turnover or market access fees will probably counter your plans.
I'm not sure I understand your question about accuracy and real-time availability. Of course it's real-time and of course it's accurate. Or do you mean if there's some sort of guarantee to trade on the last seen quote, e.g. like a FIX Order 'D' or 'E' (prev quoted, prev indicated)?