Are you dead-set on doing all-extract? If so, I would recommend rather than doing all sorghum, you use a combo of sorghum, rice extract (solids or syrup work equally well), candi syrup, raw honey, and maltodextrine. For an IIPA, the "Golden" candi syrup would be a good addition, rather than amber/D-45. Raw honey is pretty essential to getting some residual sweetness--it can really help balance out the dry twang of the sorghum.
I also recommend skewing your hop schedule toward the very late end of the boil, unless you want to use a large portion of honey (in which case, go nuts in the early additions). For beers that are all (or mostly) sorghum, it's usually best to get around half your IBUs from additions made at 15 min or later. And use a really smooth bittering hop, like Magnum or Millenium. Sorghum beers usually finish quite dry and can be easily unbalanced by too much early-addition bitterness.
I'll add the additional caveat that sorghum *REALLY* enhances the citrus flavor of American "C" hops. To the point where you will feel like you're drinking alcoholic grapefruit juice if you go overboard. Mixing up the sorghum as I advise can really help avoid that.