90/60 or so is low norm, but there really is no such thing as too low as long as you are asymptomatic (dizzy, lightheaded, syncope). Many who are used to running a significantly higher pressure (>20mm Hg change for example) would experience some of these symptoms at pressures that low. Also of course absent any major cardiac event or pathology (CHF, dysrhythmia, dehydration, shock, etc.). Hypotension is more about relativity than some specific range. What is hypotensive for one may not be hypotensive for another. Your supplements may be helping somewhat, but @ your height & weight, 5'8" 260# or so I believe you are, your BP has more to do w/ genetics than anything. Most could not reasonably expect to duplicate this by simply employing your supplement regimen.
Rex.