Hey George,
Here's a few important things to remember.
1. If this wasn't anxiety, you wouldn't be so compulsively obsessed over it. Which I know you are, because I do the same thing

Typically, people who get diagnoses with severe disorders, aren't the one's freaking out worrying about them!
2. If we knew anxiety symptoms were being caused by anxiety, NO ONE would have health anxiety! This is why anxiety always presents in ways you never think possible.
Muscle cramps are absolutely caused by anxiety. In fact, it's really common. Anxiety produces stress hormones in the body, stress hormones produce tension.
Anxiety causes that same tension throughout the nervous system, so of course you can experience speech difficulty, dizziness, jitters, tingling, skin burning, skin cooling, weakness, etc.
Your had an amazing work up, the testing doctors do are good. You have to understand, the odds of you having MS are what, 1%? The odds of testing catching MS are 99%. I'd say you have a better chance of being attacked by a bear.
I know your thinking, which is, if this is anxiety, then why does it happen when I am calm. Why does it happen everyday. If this was anxiety wouldn't the symptoms disappear for a few days when I am not anxious. Please understand, this anxiety trapped is caused in a few ways:
The brains cortex (which controls rational/logical thinking) powers down and the Amygdala (fear center) becomes activated, this propels those compulsive, fearful thoughts. The amygdala can stay active for months, years, etc. Remember this formula, even on days where you don't feel anxious:
Worry is programed into your subconscious. Sub conscious fearful throughs = stress hormones release. Stress hormones release = symptoms in the body. Symptoms in the body=stressful thoughts. So it's the thoughts that control the symptoms, that control the thoughts! Even when you feel calm, your still on high alert.
It can take a long time to power down the amygdala and have your body return to a normal stress response.
The only way to treat this, is to STOP thinking about it and thought block. You've had every test done. Get busy and stop focusing on it! Also, you can try things like chamomile tea and magniesum supplements to help with nerve function and cramping. Though don't expect this to be a quick fix. It will not overpower anxiety, it might help a touch thought. Hang in there bud and your not alone.
We all have different diseases that we're convinced we have. We all think our situation is unique! Again, if there was a way to prove that the symptoms were anxiety, anxiety conditions wouldn't exist. We'd all be calm because we "knew". But it boils down to OCD/Pure-O and us trying to "control" things we have no control over.