One thing you might not be aware of is that you can add your own listings for ingredients in BeerSmith, so if it doesn't have the specific Vienna malt you've got, but you have the necessary statistics on it, you can add it yourself. Also, if you go to (If memory serves) File->Add-ons, there are several brands' worth of additional ingredients available as add-ons, which may include the one you want.
I do agree with Daksin about the crystal malt; while I am all in favor of balance in beers, 2 lbs. of crystal is likely to be too much caramel sweetness for an Imperial IPA. Rather than replacing it entirely with base malt, however, I would be inclined to use a judicious amount - say, half a pound - of an medium-roast malt such as Victory, Biscuit, or Aromatic. This will increase the malt flavor and aroma without the heavy caramel flavor, and add a bready or biscuity element to it. Don't use too much, or it would compete with the Vienna contribution, but a half pound each of crystal and biscuit should do nicely.
You may also want to switch to 20L crystal as well, to lighten the color somewhat, as 12 SRM is definitely on the darker end of the spectrum for an IIPA - while the style guidelines generally say that up to 15 SRM is in style, 10 SRM is more typical of what I've seen.
You don't mention your target mash temperature, which is a crucial factor in how dry or sweet a beer will be. With an IIPA, you want a dry to medium body overall, so a mid-range mash schedule - say around 150-152 degrees F - is probably called for. If you are using multiple stages, a la Palmer, then you want the conversion rests to be roughly 30 minutes apiece.
Regarding the hops, AFAIK, having a hop addition at 45 minutes generally doesn't make much sense; it gets a lower utilization than at 60 minutes, but doesn't significantly contribute to the hop flavor. Also, you generally want to either FWH or use a late flavoring addition; there's not much point in doing both. Keep in mind that while FWH will technically have a higher utilization rate, the bittering tends to be mellowed out; so while the IBU rating may be high with FWH, the actual bitterness contribution will be about the same as it would be for a 20 minute addition. I personally like first wort hopping and apply it quite often, but then I am not as much of a hophead as some folks.
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