Baud is about how often you shift the modulation from one state to another, and if 200 cycles is enough for the receiver to reliably lock on to the signal, then this defined your baud rate -- you can sift frequencies up to 1,000 times per second -- 1,000 baud. A modulation scheme may have less than one or more than one bit encoded in each modulation shift. A good, reliable scheme to use is Manchester Phase Encoding, which encodes one bit for every two shifts in frequency - 0.5 bits/baud. Async serial will put 8 bits onto 10 bauds -- 0.8 bits/baud. To get more than one bit/baud you will need more than 2 frequencies or use some other modulation, like AM or PSK, or a combination. This sort of thing is something you would tackle AFTER getting the basic 2-frequency or on-off-keying system working. Personally, I would try for on-off keying with just one frequency first.