Hi and welcome. Love your screen name.
As to the hereditabilty of MS, please see http://www.medhelp.org/posts/Multiple-Sclerosis/Genetics-of-MS/show/923576
. This was posted just the other day by Quix, our resident but unofficial expert.
It's not necessarily true that your dad wouldn't have gotten MS had he not had an infection. We all get infections of one sort or other quite frequently, without getting MS. It's true that an MS relapse can be precipitated by some sort of infection, but the MS
was there all along, if not causing symptoms. I'm not at all sure that the very first symptoms of MS, the first attack, can be brought about by an infection. Possibly it could bring it to the forefront. MS is not caused by a weakened immune system. In general our immune systems are quite normal, but they get confused by what is 'its own' and what is 'foreign.'
There is a great deal of research about the causes of MS, and it's quite clear that there's no single factor. It seems that a 'perfect storm' of physical events and chemicals must come about to 'catch' a given individual while sparing the huge majority of others. In the US, the odds are maybe 750 to 1 against.
I can understand why you are so focused on small bodily sensations, yet it's possible that being focused is what's making you worry. We all have aches and pains here and there that we immediately forget about or don't even notice, but if we fixate we notice every little thing. Your problem with your fingers sounds a lot like a pinched ulnar nerve, and nothing else you mention seems MS-like.
There's nothing we can do to prevent MS. Eating well and taking vitamin supplements is always a good idea, on general principles, but there's no evidence whatever that MS can be warded off. You might see your PCP for a checkup and to have your vitamin levels checked. If tests come out well the probability is overhwelming that you are fine.
It's very understandable that seeing your dad deteriorate has caused you to worry, but focusing on that will make things worse. My advice is to live your life and not expect to become MS's next victim. It seldom works that way. I'm sure you take good care of your dad, and that brings you comfort.