If you have access to an iPad, we have had huge mileage out of the Letter School app. It's intrinsically rewarding (funny things happen to the letters) and reinforces skills like using the same starting place for the letter each time. It's helping us separate out pencil frustration from mental sequencing of strokes frustration.
ETA: have you tried having your DS use golf pencils? They're half as heavy, of course, and our younger DS prefers them...
this is why I love this board ((hugs)) great suggestions! Golf pencils would solve the other problem which makes me want to rip out his and my hair - the picking off the erasers - so not only do you have pencils with no erasers you have little bits of eraser all over the house ARRG!!!!
we had iwritewords which also emphasized where to start, which he is terrible at, but I guess it seemed to babyish? or he was just tired of it, maybe a new one would get him interested in it?
DeHe