Take magnesium too.....if you workout that is an important thing for the joints and muscles.

Dynamic stretching would be a better choice...Could be a fascia or tendon issue. Have you ever injured your feet, ankles or knees? Footwear could also be playing a role in your calves cramping. Is the cramping in the large muscle on the back of the calf? Is it lower? Is it higher? Side? Several muscles make up the calf...too hard to tell you why you having the issues. Are you running on your toes and not landing on your entire foot? You may need to focus on firing other muscles within the calf while you're running....A massage therapist that works primarily with athletes and practices sports massage, a Licensed Athletic Trainer, or a really good personal trainer with a Kinesiology degree, not just the certification, would all be good sources to consult.

Interesting...I wonder if there has been some damage to either a tendon, or to a nerve that's causing the muscle to essentially misfire and go in to a spasm...you say the entire calf, I'm going to assume you mean the gastrocnemius (largest muscle on the lower leg...basically that big muscle most refer to as a calf)...it's the coolest muscle in the body to say and spell. It's also one of the foundation muscles, so rather important...I had a client with calf spasms when they ran, but it was an ankle issue that I corrected in a couple of sessions, but theirs was not as severe as yours, and it was not bilateral. That's the part that I find most interesting. Please keep us informed as to what they determine, and if it gets corrected.

The sciatic nerve is essentially a rope of nerves running up both legs into the glutes and then into the spine. I wonder if you have damaged something higher up...So many possibilities. The human body is a fascinating, and at times disgusting, thing...

Based on your weight and existing problems, I would forgo running.
The number one question that is seldom asked is "what is your goal?". Is it simply weight loss, overall strength, muscle building/body building/physique, sprinter, marathon/endurance sports, etc.?

You have two goals - weight loss and increased cardio. I would assume that you want to preserve your existing muscle and strength. In my opinion, cardio can be obtained quicker than muscle mass, overall strength, and healthy weight loss. Therefore, I would focus on weight loss first, which can be attained simply by establishing a healthy caloric deficit. Your weight training will provide some cardio, accelerate the weight loss, and ensure that muscle loss is kept to a minimum while operating with a caloric deficit. You can still do some type of cardio - many ideas have already been suggested. However, I would keep it at a minimum. It seems that you have built some strength and muscle. If you are eating less and overdoing your cardio, there is a good chance you will lose some of your hard earned muscle.

You can go cardio crazy, slash your caloric intake and easily lose 5 pounds a week, but that would not be healthy.

I know this is a big tangent from seeking help for a calf cramp, but hopefully it is somewhat helpful.