Let's see, how many college classmates can I describe that fit that exactly? :-)

They couldn't write essays easily, thus those classes were "boring" and "pointless" and "why do I have to take this D@** class anyway since I'll never use this?"

He's a little young for this now, but over time, a useful skill will be to help him find the interest/value in an exercise and to meet it within the rules, but also in a way that pleases him. For example, I used to write elaborate and dramatic sentences for spelling/vocabulary rather than the shortest, dullest, possible sentence. I remember vividly an incident where I wrote something like, "The visitor dropped the magnificent archetype and it shattered onto the floor." The teacher took me aside to explain to me the difference between 'prototype' and 'archetype' (archetype being the prototype of an idea, like a character or plot, rather than a tangible item) and thanked me for writing such an expressive sentence that showed her that she had not defined it well enough for the class.

DD is getting bored with some of her homework, so I add extra rules like, "I bet you can't finish this page in 4 minutes, GO!" or otherwise try to find patterns or other strange things. Sometimes she does it upside down.

It sounds like you're going great with him, Hillary. Having a child that gifted is like the Chinese curse, "May you live in interesting times." It is a challenge, and he (and you) may struggle. But, keep supporting him and he'll find a path to a productive and happy adulthood.