well, with 6.6 lbs of LME, you'll be at about 4.5% alcohol.
Normally I'd say that is too much Crystal, but it's a light crystal (10L) so it should work.
I think it looks fine.
You can use hallertau and cascade together. In regards to flavor, Hallertau is a little more spicy/fruity, cascade is more citrusy/grassy/grapefruit. Cascade probably has a alpha acid content.
You could even blend them both through the whole brew. That would probably give you some nice characteristic from the cascade while smoothing it out with the hallertau.