Note that the DIN port can be used either as a serial or as a standard packet data port with support for packet at 9600bps. I don’t think you’ll be able to do better than 1200bps using the mic port.
For clarification, according to the TM-V7 operators manual, Page 12, Pin 2 or RD is listed as NC:No Connection. I was unable to get any audio from that pin into my Digirig.