Thanks for the advice, everyone-the suggestion that I hadn't heard (and thus hadn't tried) previously was to only WDT the top ~half of the grinds before tamping, and that seems to have helped (that + a new coffee, possibly...). So right now what I'm doing is:
1. Grind into jar
2. Shake and tap jar to get everything loose
3. Put basket on top of jar; flip to empty
4. Shake side to side to level
5. Rake top to remove clumps
6. Tap on counter
Easier done than said, in this case, but best to list it all out I suppose. I think that these have been the best so far! The first video below is at a 6 on the C40, and the second is at a 7, both at a 17:38 ratio, pulling in ~40 and ~30 seconds respectively. Kind of thinking a "6.5" might be good, as the 7 pulled a little too "easily", by feel... the red clix is staring at me, but I'll keep playing around with this for a while.