You can slot up to about 70% recharge in Build Up/Aim and still have a 90% chance to proc Gaussians, and OP has put lower-level IOs into BU to keep it under that threshold.
Shiver is largely redundant with Snow Storm, and and Snow Storm is also the better choice than Flash Freeze. And you have to take either Flash Freeze or Snow Storm to get to Ice Shield and Hoarfrost.
The OF proc is both a KB-to-KD and Knockback proc; it adds chance to Knockdown to any attack, in addition to reducing Knockback.
As for your build, OP, you should shuffle around some of your slottings. Overwhelming Force doesn't give especially good +Recharge, so you should move it from Blizzard to somewhere else, and put in one of the ATO or Winter sets. I like OF in Frost Breath, since the KD proc gives it some decent crowd control ability. I have an Ice3 Blaster myself, with a pretty similar build. You can check out her build here if you want some ideas. I noticed your build is made to have some defense; my build didn't attempt for defense at all beyond taking and slotting Ice Shield and Hoarfrost, and it's still a surprisingly survivable build.