You are close - stick with normal polarity and go back to LSB.
Make sure you have this:
http://www.ascii-code.com/Make a test text file in a simple text editor on your PC.
If the PC has a RS232 serial port use your scope probe to connect to the TX and GND pins on the port.
Use a terminal program on your PC to set up the parameters (speed, # bits, stop bit, parity, etc.). Make sure to turn off (hardware) flow control. Transfer/Send the text file (if you make the file long enough and send it at a low speed like 2400bps you will have plenty of time to twiddle with your scope settings).
Set your scope for the same parameters, including normal polarity and LSB. Start with ASCII on the decoder (vs. Binary or Hex or Decimal. ASCII characters are easy to recognize/read). Once the characters read properly (in ASCII) change to Binary and then you will have confidence that the Binary is correct (plus you can confirm it with the ASCII Table).
Have fun.
PS, notice on the individual Binary characters (such as the u and the m below) that the number patterns (1s and 0s) go the opposite direction of the waveform patterns. The number (bit) on the right side of the Byte in the Binary sequence is depicted by the left side of the waveform (1s are open on the top of the waveform and 0s are closed on the top of the waveform). It's probably easiest to see on the Binary m.