I'm not sure what you consider too low, but my blood pressure averaged 83/65 for at least 7 days towards the end of my 36.5 day fast. If one day it was suddenly 73/55 i would have been alarmed (and would have viewed that as a warning sign to break the fast) but it remained very steady. My normal bp when eating is about 110/70 and i couldn't be more delighted with it :p.
I strongly prefer to let my body be in control when i fast and believe that it knew what it was doing in calming my bp to such an extent, conserving its energies fantastically to optimize the cleansing and healing that it was doing so amazingly well. The very last thing i would want to do is drink salt to interfere with that.
If you will permit me to borrow one of your favorite expressions... "but hey, it's your body, do what you want" ;). You're doing a good job here, good luck as you continue.