I'd use at least a pound of corn sugar to make sure you finish low enough with all that extract. Also, since this is your first big beer I have no idea how much of this you already know but here goes:
Make sure you make a starter or at least buy enough yeast. Check the mr malty website for a reference. This is the most important thing!
Big beers get really warm so have some way of doing temp control. A swamp cooler with frozen water bottles at the very least.
For my big beers I like to try and keep the yeast in suspension by genteelly rocking the carboy back and forth without splashing much for at least a minute. I do this two or three times a day after visible signs of fermentation have stopped just to make sure the yeast don't floc out on you.
Don't dry hop right away, wait until you are about ready to bottle/keg. I mention this because I used to leave them in there for months at a time before someone told me otherwise.