It's basically down to formulation of the recipe. If you don't balance all those extra fermentables with hops and other non-fermentable malts you'll end up with a nice roasty rocket fuel.
The other key is aging. A big beer like that needs a lot of aging time (6-9 months most likely) so you need to be patient and let it age. If you post the recipe we can help you out on that front, the patience is up to you though.
I don't have the values for the Coopers extracts so I can't figure out your OG. I very much doubt 1oz of bittering hops will be enough though given the gravity range this beer should hit. Hopefully someone with those numbers will chime in.
I'll be honest I'm not that familiar with gallons as a measurement and I do everything by weight anyway. Best thing to do since this thread title won't generate much interest on the recipe, is post your full recipe to the recipes forum and that will get you help making a nice balanced recipe.