I know this is an old thread. But I know who the J J Mcdonald is that you guys are struggling with. He is my Great Great Great Grandfather, John Jerman McDonald . In fact I have a picture and he even put 9th Cavalry on his tombstone which is in Snowhill Baptist Church Cemetery in Collin County.

Here's a link with all the info:
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=6923717

Thanks!