Looking at this from a couple of angles....
Two gallons of Trub loss is huge. It's 15% of your volume. That means that even if you get 100% mash efficiency, you are only getting 85% Brewhouse efficiency (aka sugar into the fermenter). Is that accurate to what you system does? Is there any way to reduce this loss?

I do see that your equipment settings expect 70% mash efficiency, which is reasonable.
I'm thinking that mash chemistry is an issue.
For a beer this pale, a mash of 5.2 to 5.4 would increase extraction. As-is, a half pound of acidulated malt would help.
The calcium level could be higher. Perhaps at least 6.5 grams gypsum and 5 grams chloride. Along with the acidulated malt, this would be very close to 5.2 pH.
The mash could be thicker. A thicker mash will hit pH easier and allow you to reduce the acidulated malt by 25%. ...Mostly, this is my opinion, but with well modified grains you only need single step and only 1.1 qt/lb. This gives you plenty of room in both space and temperature for a mashout infusion.