You don't have to use lager temps with that yeast. The cooler the better, of course, but you can use lager at ale temps
If I were you, I'd just mash everything in the low 150s. Throw in as much of that Northern Brewer as you'd like. Some would do one addition, some two, some three. It depends on how bitter and hoppy you want the final product. I'd bet it'd be good with a moderate bittering addition, a moderate flavor addition around 20-30 minutes and a good dose of aroma hops in the last minute or so.