As far as the magnesium citrate goes, I don't see any reasons to stop taking it either. There have been cases when I've forgotten to take it for a day or two and I can feel the difference in the morning after a heavier workout.

As for your hands, given that you are focusing on upper body workouts maybe one up your protein intake, see if that improves things. Unless you are a vegan, Icelandic yogurt(skyr) is a pretty solid solution(the unflavored kind). In terms of consistency, I'd say it's similar to Philadelphia cheese but almost tasteless. 1 yogurt a day (350g) made a dramatic improvement in my case. Not sure about the US(judging from the fact that you used miles), but you can find those in almost every grocery store in Europe at this point for around a euro.