American special bitter with Northern Brewer?

I need to brew a small batch (probably 1.5 gallons) of something to test my efficiency since I am just starting to crush my own grain and use a different mash set-up. I also want to grow some yeast, so this might just be a starter that I can drink. I was planning on using 2-row base, and have been interested in trying to brew something closer to a session strength ale like a mild or bitter. I came across the recipe for Stone's West Coast Bitter which is:
Rahr Two-Row 88%
Cara-Pils 5%
Crisp Crystal 77L 5%
Honey Malt 2%
US05 (the yeast I want to grow)

I have the crystal to use, but not the others. I bought some crystal 77L, 120L, and choc to play with in experimental recipes to get an idea of the flavors of each. I have Vienna and Crystal 10L as well. I also would like to use up .5 oz of Northern Brewer I have in the freezer so I'm not spending any extra money on hops, and that would be a great chance to get an idea of what that flavor is like as well.

So if I do something like:
88% 2row
7% vienna
7% 77L

and shoot for an OG around 1.047 (at 75%) and hop more like an APA with only NB to 35 IBU, will I come out with something decent? I am thinking if I get better than expected efficiency, it'll be a standard APA. If I get worse efficiency, it'll be more of a special bitter, American style.

What mash temps should I shoot for? Any better ideas with the ingredients I have on hand?