I'll be surprised if you can get that thing to drinkable levels. Extract can be hard to attenuate sometimes anyway, but that much extract is gonna take a lot of coaxing, doing everything right...and you're probably going to need to pitch a healthy starter of a high gravity yeast as well. Two vials going into that is probably 3 vials too few. You needed to use both of those vials in a 5.3L starter to have enough yeast. If pitching only vials, you needed 5 vials to start with.
I have no problem with experimentation, but what possessed you to put 12lbs of extract into 5g of beer?
Edit, I'd go buy 3 more vials of yeast right now if you can, and if you have a way of oxyegenating it, I'd use a metric sh!t ton of 02 as well.
First Brew was thanksgiving 2011, I'm at 93 batches and counting (as of 8/17/2014), and ran out of room in my signature to list them all.