Both the 5-pin and 3-pin DMX connectors use balanced signaling. The two extra connections on the 5-pin plug are not used (see http://pinouts.ru/Home/dmx-512_pinout.shtml). So, yes, I maintain you can use a simple passive adapter to go to 5-pin if you need to.
The DMX signal is generated by a custom FPGA core (not a hacked UART), which produces a correct break and not a "framing error". Feel free to check our Verilog source (online at Github) if you have the slightest doubt about this. If you can find bugs, we'd be happy to fix them and push out a FPGAs bitstream update.