My DS also had a huge point spread, 60 points or so. We notice he is much better at fine motor things if he is not using a tool. For example legos and playdoh do not require a tool. Also he is not too bad at touch screens, though I think a little slower or clumsier than many kids his age. It had been explained to us as fully due to dsygraphia/DCD that was just amplified with the addition of the pencil/implement. OTs have been trying to integrate his sides and develop his core strength and so on. With no visible progress that I could see.
But then finally we saw a doctor who diagnosed him with loose or hyperextensible joints, in which some or all of the joints are able to bend past the normal angle. In retrospect some of his difficulties are due to this. He does also have difficulty with motor planning or just personal planning in general, add type issues, and he's not the strongest looking person. So for him it's multiple causes. If you are built faintly like a marionette (that would function best if someone was holding them up), then even mild ADD etc is going to effectively be a lot worse. Another term applied to this is Ehlers Danlos, sometimes used to describe anyone with loose joints, but more usually used to describe a person who either has more marked bendiness or other associated issues.
While my DS scores high on the "Beighton score" and clearly fits into the syndrome category, it's really not something one would notice just looking at him: he's not going to win a yoga contest, and lots of children are quite flexible. Many of the photos even of mild degrees of joint laxity seem extreme compared to him. However, specifically when he holds a pencil and attempts to write one can see his little fingers curving noticeably in ways mine do not when I write. Actually just holding a pencil looks okay, it's when he applies it to the paper (pressing down) that I see bending to his fingers.
So something to look into if legos/playdoh/ipad comes noticeably easier to him than writing/forks+knives.
