Problem solved. Thanks for all of your help.
As a side note, I went to the Ford dealer service department in Farmington ME and asked for Mercon ATF. They said Ford no longer makes that and that I'm supposed to use Motorcraft Power Steering fluid instead. I explained what I was going to use it for and they said that it is a replacement for Mercon V. Kind of confusing to me because I didn't ask for Mercon V but Mercon ATF. I guess they are the same.
Anyways, all is quiet with the breaking system again and I could find no leaks to explain the loss of fluid. It ended up taking about 14 ounces.
Thanks again for all the help.