.5lb of cocoa is way too much. Try adding a few oz to secondary along with the vanilla and other spices. Cinnamon is a powerful spice, try using some cinnamon sticks in secondary. You can always rack out of secondary when flavor gets to where you want it.
You might need to use more than one packet of dry depending on your OG. Use Mr Malty http://www.mrmalty.com/calc/calc.html
Don't foget to rehydrate the yeast.
I would ditch the carapils and the malto dextrin, they wont add malty flavor. Don't worry about head retention and mouth feel as crystal malt and mash temp will have the same effect on head retention and mouth feel. Its just a matter of picking crystal malts to match the malty flavors and...
Sounds like fun.
I have never used Nottingham in an IIPA, but it should be alcohol tolerant enough to get the job done. Last one I made I used Northwest Ale. By all means keep the crystal down as it can be distracting when used with too heavy a hand in this style. To keep it from being...
I have used coffee malt, but enjoy the flavor/aroma of cracked coffee beans in secondary more. Cold steeping the coffee for a day and add that at bottling is another method.
You could. But if you would rather not dump the "foreign" wort into your beer, you could toss the starter in the fridge to settle out the yeast then pour out the liquid on-top of the settled yeast.
Oxygen exposure and heat will degrade the potency. That said, try breaking one open, make some hop tea see what its like. If its still good, vacuum seal them if you can or freezer bag them and keep them as cold as possible till use.