There are some reports of FSH causing disturbances of the heart's conduction system. Arrythmias called atrial flutter and atrial fibrillation are the most likely problems to occur. Atrial fibrillation can be associated with stroke from embolism from the heart, fainting spells, chest pain, and potentially sudden death. All that said, serious problems are probably uncommon. If someone has falls so often that walking is just dangerous, then exclusive use of a wheelchair makes sense.
Some reports describe accumulation of a compound called beta amyloid.
So far as I known, Coenzyme Q10 and Carnitine are not helpful. I have seen a number of people who have had PLS but none of them had any affected relatives. When two close relatives are affected, then there has to be some chance of a genetic basis. If neither of your husband's parents is affected, then hopefully, if there is a genetic cause, it is a recessive gene and your children will not be at risk. If the diagnosis of PLS is correct, then they need to be studied to look for a genetic cause.