All I can say is to give it a try. Maybe in your case it will not be to much of a problem if communications do not work every time. Just try sending the score again??

The MAX232 will not help you.

If you find it works part of the time, you may try 2400 baud. Sometimes a slower signal is more reliable and more tolerant.

I am not sure, the internal on your chip might be able to be calibrated. Some one else will have to help you if it can or needs to be.