Brooklyn summer clone (extract plus specialty) recipe tweaks?

My wife wants me to brew a lighter drinking English style beer in anticipation of better weather. We both Agreed a Brooklyn summer clone might be good.

I looked through my clone brews book and they had the following recipe. The og/fg and hops listed appear to be close to what is listed on Brooklyn's site. I have listed any questions next to the appropriate ingredients listed. Feel free to add any other tips or thoughts you may have. Note I have not run this recipe through any software to verify values listed.

Brooklyn best bitter
Og:1.046-1.047
IBU:32
SRM:7
Abv:4.5%
5.5 gallon boil (due to increased volume compared To the original recipe my hop amounts may need to be reduced, boil volume in orig recipe is only 2.5 gallons)

6oz 55L British crystal
4oz torrified wheat (my research indicates this may need to be mashed. If so is there something I can substitute like a 1/4 or 1/3 lb of wheat DME for the extra light DME listed below?)
Steep these at 155f for 30 mins and rinse grains with 1/2 gallon water155f Once steep complete

5.33 lb Extra light DME (1/2 at 60 min the other 1/2 w/ 15 mins left)

1oz Perle 60 min
1/4 oz cascade 15 min
1/4 oz fuggles 15 min
1/4 oz Amarillo 15 min
1 whirlfloc tablet 15 min
1/4 Oz fuggles 5 min (or flameout?)
1/2oz Amarillo 5 min (or flameout?)

Should I dry hop with the remaining 1/4oz of Amarillo, 1/2oz fuggles, and 3/4oz cascade or will this turn this beer into a straight hoppy pale ale rather than a best bitter?

Yeast either safale us04 or Nottingham (orig recipe suggests wyeast 1968 or 1028...which dry yeast is a better substitute?...I will likely be fermenting in the high 50s or low 60s)

Thanks in advance!

 

Is there something else i can use to substite for the marris? Or should I try my hand at a mini mash using it? If so how do you suggest I proceed?

 

Thanks guys I saw that there is Marris lme. Not sure if my lhbs carries it or not.