i would reduce or eliminate the carapils and go stronger/all the way caramel. you'll get plenty of head retention from the caramel. i'd consider bumping up to C-60, if that's an option. you are currently at 10% crystal, you could increase to 15% by adding another half-pound.
btw, with that much hops there is little hope of being balanced - you are making a hop-bomb. balance isn't an option. it's like saying you're making suicide wings and you want to be sure the chicken taste comes through
do you need to dry-hop with cascade and legacy, only? i'd consider moving some hops with even better aromatics like simcoe or citra to the dry-hop stage.
finally, i would use the only columbus for bittering (use as much as needed to get the right IBUs) and save your mix of everything else for the last 15 minutes. so something like:
2 oz columbus @ 60 mins (or whatever amount required for the desired IBUs)
10 oz mega-mix continuously added from 15 mins to flamout
dry-hop with simcoe & cascade