Hello, Andy and Welcome to Neurotalk.

It is hard to say on the net what is going on with you.

But I will say these general things may cause twitching:

1) low blood sugar (or very high sugar which is not getting into the cells of your muscles) About 70% of people with low blood sugar attacks report twitching.

2) low magnesium levels will cause muscle twitching

3) generalized weakness can be from low blood sugar, or an autoimmune disorder called Myasthenia gravis. This usually shows recovery after resting, as it starts up.

4) people with osteopenia may have low Vitamin D levels. I strongly urge you to get a blood test for this.
Here is a video to watch:
http://www.youtube.com/watch?v=TQ-qekFoi-o

5) Low B12 levels will cause nerves to not work properly and neuropathy is an early sign of this. A blood test for B12 will show if you are low. Anything below 400-500 should be supplemented. Many doctors use an antiquated range showing lower normals. Don't accept this interpretation. You can have this test done with the Vit D test.

These are the most obvious things to start looking at. But with your complex history of serious medical issues, there may be other more difficult things going on with you that will require a doctor's examination in detail. For example some visual and ear symptoms with arm numbness may be from an congenital condition called Arnold Chiari. An MRI of the head and neck will show if this is the case for you.