It sounds to me like you have done all the right things...particularly the epsom salts bath. Magnesium is needed for charley horse type pain, I believe.
Yes, I would suspect a parasite, given your symptoms, and other experiences...although I am no 'authority', of course.
Good for you for not panicking, and for doing all the right things.
Perhaps you could find a parasitologist...or even a good vet, just to consult. An extra opinion never hurts...though you might surprise the heck out of a vet!
Still, he or she might be very proud that you asked.
I have had some 'symptoms' in the feet and arms, even a finger or two, and some on my tummy...though nothing like yours. If mine are parasites, they have taken quite a while to materialize...like a year and a half.
I also have suspicions of toxins, perhaps in tiny encapsulations, but I can only guess.
You know me, I think a bath or footbath in a 1% solution of clean, whole mineral salts, is a good thing for anyone, because I think that whole mineral salts are the basis for life. Organ support is a good thing, I believe, and the skin is a fine selector and balancer...no need to calculate, once you have a 1% solution!
The skin takes in and pushes out exactly what is needed, plus it dilutes toxins. And the solution is sterile...no one can 'catch' anything from you, even if the tub isn't washed afterwards.