Not that I’m an expert, but I wouldn’t expect thyroid ups and downs to affect spasticity. (I have had an overactive thyroid and now am underactive.)
How much Baclofen do you take? And have you tried magnesium oil applied topically to your leg? Many people use it for precisely this problem.
I take Baclofen (between 60 and 80 mg per day) and also use Cloneazepam for spasticity, primarily in the afternoon, evening and before bed. It isn’t completely spasm proof, and the Cloneazepam wears off by morning (so I wake up to painful spasms), but it’s bettr than just Baclofen alone.
I wouldn’t have expected a doctor to prescribe Diazepam on a long term basis because of its habit forming potential. For some reason they don’t have a problem with Cloneazepam. But then I’ve been using it for several years and the same dose still works for me.
There are other drugs you could try for spasticity, some people use Dantrium (Dantrolene). You might be better off trying a different drug like this if Baclofen isn’t doing it for you. Or try and change the times you take your Baclofen. Work out when the spasms are at their worst and take the Baclofen in time to stop the spasms from starting. I have found that taking Baclofen to prevent spasms is more effective than taking it once they’ve started.
Best of luck.