Sorry I pounced on you! I doubt that helped either of your runs.. I couldn't help it though, you're entirely too pouncable! ;)
Ten years ago when I was young middle aged old fart like you are now I used to have lower back problems. Those were always related to butt muscles and for me the best way to keep them away was butt stretching. But I had to do it before the back pain appeared, when pain was on it was too late. Chiropractic, massage and full rest did help.