a) stop taking supplements and start looking at getting a very clean diet.
b) stop stressing! you are raising your blood pressure right now. you have to get it in your head that you will become a healthier person. mindset is big time.
c) start getting some regular exercise....cardio helps! if you haven't worked out in awhile, don't go jumping head first into the ocean without a life vest. Take is slow. Dip one foot in at a time and wade out into the water comfortably.
d) are you holding your breath during your repetitions? that will make your blood pressure go up like crazy (I know from experience...I have racked the weight and passed right the fuck out on the platform before). make sure you are breathing and yes, all the factors that you listed for making your BP 140/96 play a contributing factor.
e) yes, tons of people workout just fine on beta-blockers. I have trained a lot of people on beta-blockers and, one of them happend to be a tri-athlete. All we had to do was be concious of how she felt (her rate of preceived exertion) because the beta-blockers keep your heart rate down, and it would be impossible for me to know how hard she was working looking at her heart rate.
Hope that helps!