Hey Lestro! I just registered so I could respond on this thread! I love what you're doing so far.
Your card effect example seem good so far. As for the spell list, I'm not ENTIRELY sold on the 6th level spell cap. Both because there's Cards that arguably go over it, and because Sakura was meant to be the most powerful magician in the Clamp Multiverse after succeeding Clow Reed (and given that dude has Wish as a spell-like ability, WOAH).
Then again, I understand the need for spell balance. But if you're going to put a cap on the spell levels instead of allowing 9th level spells, I would put the cap at 8th level. Minimum.
But that's just me.
Also, fun fact. You're actually not the first person on this board to attempt a Cardcaptor class, though yours is more detailed. kwanzaabot posted a build in 2008. It's here