I like the Gp idea, and mashing at 154 will give you some more dextrins to help overcome a lack of crystal.
I don't like your hop schedule. FO and DH choices and amounts = awesome!
Magnum at 5 yeck
Simcoe at 10 = awesome!
I would say you need to at least double those late additions, use something other than magnum late (early is where its best) and maybe even consider moving the 10 to 15.
2oz Simcoe at 15min
2oz Amarillo or Centennial at 5 min
then what you have listed at FO and DH.
Reduce your 60min Magnum a bit to account for the IBU contributions of more late hops.
1450 will work well with this I think, particularly since it leaves a fuller, maltier flavor than chico, and being that you're using one malt, I think it'll complement nicely.