Good Lord that's a lot of questions. First things first, read this, it won't take that long, and it will answer most of your questions, plus a lot of questions you haven't asked us yet. How to Brew - By John Palmer
Second, you will definately need more extract, at least twice as much as you have, and that stuff in the can probably expired like 6-7 years ago, and even if it has no expiration date, I'm sure it won;t turn out good.
Third, 7.5 oz of different specialty grians is probably going to get you next to nothing in tems of additional flavor or color. You will probably want AT LEAST a pound of specialty grains, and depending on the grains you picked out, some may need to be mashed instead of only steeped. (really not that hard)
Fourth, you are going to have a difficult time reaching 30-40 IBUs anyway, unless you are boiling the entirething (all 6 gallons or so on the stove). Simcoe will give you MUCH more bitterness than Cascade, but I do like Simcoe to finish. Cascade isn't really a bittering hop, and you may be better suited going with a higher AA% hop to bitter with.
Twenty-Second, or whatever number, if that didn't make a lot of sense to you, or raised more questions, I again refer you to How to Brew - By John Palmer .
Welcome Eric, happy brewing.