Statistics note that we living kidney donors have a tendency to develop high blood pressure in the years after donation. So, as you noted, borderline high blood pressure now would exclude you from being accepted as a kidney donor by most hospitals, although some hospitals stretch the limits. If it were not for the blood pressure you could probably donate and continue your military career. Over the years several military people on this site have donated a kidney and returned to active duty.
Letting as many people as possible know about your mom's need would be wise. Some patients have received offers of a kidney from neighbors, family, friends, coworkers, old alumni, church or synagogue members, waitresses, manicurists, etc. It is surprising how many people donate once they hear about a need. This does mean giving up some privacy, but it might result in some offers. You did not mention her age, but older people can donate. I donated at age 56, about 13 years ago. Many hospitals prefer a donation between people of similar age. Facebook can be a good tool, especially if you can get people to pass on the message about the need to their friends.
Living kidney donation does have its risks, and some donors have suffered long term complications, so it should be mentioned, and potential donors should be advised to get themselves well educated about the risks before committing. Some hospitals do a good job about warning potential donors about the risks, other hospitals do poorly in this.
Well, that is all I can think of at the moment.
best wishes,
Fr. Pat
P.S. The National Kidney Foundation
www.kidney.org organizes many Kidney Walks all over the counter to help raise awareness, but I do not know of any longer races.