1960s Diagnosing of MS

In my quest to find out more information on my own family history it has occurred to me that my grandmother's last years may be been misdiagnosed as debilitating arthritis, when it fact, it may have been multiple sclerosis. In her later years, all she could do was go from the bed to her chair for the day with help, eat drink, and watch a little tv. I was only six. My symptoms are that at 19 I could barely turn over in bed without using my arms to pull me up and put my legs on the floor. Walking was extremely slow and labor intensive. Back when I was 19, I attributed it to the humidity of the NE and arthritis. It eventually subsided and I moved to the South. I am 46.
Now, those symptoms are coming back along with others such as the squggly line that turns when I look at something, a hugging feeling through my back and pain in my lower hips. This has gotten worse over the past three years. A brain MRI shows nonspecific punctuate signal abnormalities.
I have two questions:
1) Is relapsing/remitting MS inherited?
2) Was MS often attributed to arthritis back in the 1960s?
3) Are there further tests that I might have because the pain is severe?