I'll take a crack for you...
1 - Your 2-row base malt is where you're going to get most of your fermentable sugars and thus your ABV potential. The 2# of other malts you have will have some fermentable sugars, but they are primarily for the flavor.
2 - If you're concerned about the viability of your yeast (and really, even if you're not) make a yeast starter. If it kicks off strong and really starts to floculate, then you're golden. If it is slow, you may have to boost it a few times, but you'll get off the ground and have something ready to pitch. If it doesn't kick off at all, well you've only wasted a yeast starter and not a whole batch.
3 - It's going to be very tight, if it fits at all. I've done 11# in a 10gal cooler and had plenty of room, but I'd guess it was more than half full.
Building a Bad News Brewery - eHERMS
5gal Scottish Wee Heavy
15gal American Pale Ale
20gal Belgian Wit (10 dumped)
Keg 1: Apfelwein
Keg 2: Belgian Wit (Failure)
Keg 3: American Pale Ale
Fermenting: Belgian Wit (Take 2)