interesting post.
I cant comment much on the gluten or undermethylater topics, but I will say that all my research into muscle spasms led me again and again to magnesium as well.
I will share some thoughts with you, tho ultimately its nothing you dont know. You may know more than I do in fact.
Basically I agree.. magnesium serves as a calming mineral. I also agree (and yes I read researchbygeorge many times also) that taurate is the optimal source. I actually have magnesium glycinate and also something called Magnesium Optimizer which is 100mg mag citrate and 350mg taurine per pill. George warns against glycine for ppl with palpitations (my main problem along with comorbid anxiety/panic and some minor OCD that is so slight most people dont notice).

Im not sure what research led him to believe that taurine is better than glycine for calming the nervous system, but I have no reason to doubt him. Im fact, if we consumed more organ meats as our ancestors did, we would get much more taurine in our diets than we do today.

Another component of the inhibitory neurotransmitters to keep in mind is GABA and anything that acts on those receptors - such as neurontin i believe and some others may have an effect on your spasms. GABA by itself supposedly cant reach the brain in any effective quantities. But gaba combined with lots of inositol can.

Something Ive noticed is that when I was first treated for anxiety they tried me on Lexapro(a a SSRI - which acts on serotonin levels), and Ativan(a benzo) simultaneously. The result - the first (and only) few nights I took it, I layed in bed literally shaking from the muscle spasms/ tremor.
I discontinued the SSRI, and switched to xanax from Ativan and either by coincidence or not it greatly relieves my muscle spasms.

Sorry Im not offering much constructive here for you other than my story, but I too continually come back to the Magnesium issue and how supposedly we are all very deficient in it.

Have you considered having an intracellular magnesium test performed?
I assume you've had a blood chemistry panel during your ordeal, but as Im sure youve read the intracellular is the way to go. I have not done it yet personally.