Handwriting is faint and it's barely legible due to wrist pain. could it be the lack of use finally sneaking up on me?

Neuromuscular proble: I can only speculate as to the cause of your problem. Common things being common, i might consider carpel tunnel syndrome (does your hand go numb when you try to write), thoracic out syndrome will cause a similar problem. Are there other parts of your body that don't work the way they used to? Pain in the wrist certainly suggests arthritis. Did you ever injure your wrist in the past?

Concerning: If your muscle atrophy is this advanced, it warrants a doctor evaluation.