I was always more partial to DME rather than liquid as it seemed to attenuate better. Also a percentage around 5-10% of plain table sugar is highly appropriate in a IPA. As far as the recipe in general and my opinion on the malt bill, I am a fan of uncluttered malt bills so I would probably go with amber DME, and a combo of C60 and C120 to get the color I wanted. 3 ounces of RB is going to give you a very distinctly roasty flavor that would take this out of IPA territory.
Here, take a look at this. I think it might be the color your looking for, and may be a better starting pint for what you're trying to accomplish.