Though he is not an expy, your character fits too many conventions to be called completely original. Please note if I sound brash, I'm not insulting your work or you and I'd feel terrible if you interpreted it that way. Its constructive criticism.
His motivation is to stop the empire and protect is loved ones, but why? Why does he stay and fight? What stops him from gathering up his loved ones and simply leaving? You said in the character sheet he was a nihilist, so why does he risk so much for what he sees as a hopeless cause? the only answer I could think of is a Hero Complex, which is almost never played straight anymore, so unless you plan on deconstructing it then I'd suggest you ensure that out of Fight or Flight only fight is left.
You also mentioned his minor motivation is knowledge. But why? This is the same motive almost every mage in fiction has. But why does he collect knowledge? No one just collects it for the heck of it, or we wouldn't need truancy laws in school systems
. Does he simply enjoy the topics he likes reading about, are they a passion or a hobby? Does he see career possibilities? Some examples of how to go deeper: Edward Elric collects knowledge on alchemy because its a chance to bring his mother back to life. Rincewind collects knowledge on "cruel and unusual geography" because it fills the hole formed by his lack of actual magic. Snape threw all his effort into potions because it was the only thing he thought he was good at after years of bullying.
Your characters hatred of strong, but less intelligent people is somewhat of a cliche now. I'm going into tons of detail here because I like to derail every author away from "dumb jock" before they get entrenched in it (its usefully in some contexts, but its overused). What kinds of dumb people does he hate? Do they have to be dumb at magic, or just dumb in general? Does he hate all stupid people? or just ignorant rude ones? What if he meets a stupid but friendly person? Or a smart person who prefers brute forcing things out of laziness? There is almost no such thing as a person who is dumb at everything. Old man Nakata from Kafka on the Shore was borderline retarded in terms of IQ, he couldn't even read. But he had his life figured out and was apparently a skilled craftsman when it came to making artisan furniture, and he had an attention span other people would kill for.
As for his weaknesses, you should be more specific. Rather than just "smart but weak", how is he weak? Does he run out of breath easily? Does he lack proper coordination? Is it easy to catch up with him and pin him down? This makes conflicts go from predictable to interesting. If he can outrun anyone the big bad sends at him, what if they eventually send a veritable marathon runner? If he instead lacks endurance, wont he struggle with all his will to end the fight quickly before he can tire out?
Overall, if you want to avoid expies or cliche archetypes here is my advice: Form the character first. When he is completely done and sorted out you can break him down into tropes if you wish to start considering deconstruction and aversion and whatnot. But if you force yourself to a template of tropes, then you will never get out of the template.
Tropes are indeed tools, you should choose the job before you choose the tools.
PS:This post was way longer than the one I thought I was going to write.